diff --git a/action/operators.py b/action/operators.py
index 3bbbac8..6554252 100644
--- a/action/operators.py
+++ b/action/operators.py
@@ -1032,7 +1032,7 @@ class ACTIONLIB_OT_store_anim_pose(Operator):
             modified=time.time_ns()
         )
 
-        lib.adapter.write_asset_description(asset_description, asset_path)
+        lib.adapter.write_description_file(asset_description, asset_path)
 
         # Restore action and cleanup
         ob.animation_data.action = current_action
diff --git a/adapters/adapter.py b/adapters/adapter.py
index c4e4a67..f9203fd 100644
--- a/adapters/adapter.py
+++ b/adapters/adapter.py
@@ -1,8 +1,9 @@
 
-from asset_library.common.functions import (read_catalog, write_catalog, norm_asset_datas, get_catalog_path)
+from asset_library.common.functions import (read_catalog, write_catalog, norm_asset_datas)
 from asset_library.common.bl_utils import get_addon_prefs, load_datablocks
 from asset_library.common.file_utils import read_file, write_file
 from asset_library.common.template import Template
+from asset_library.constants import (PREVIEW_ASSETS_SCRIPT, MODULE_DIR)
 
 from asset_library import (action, collection, file)
 
@@ -18,6 +19,7 @@ import json
 import uuid
 import time
 from functools import partial
+import subprocess
 
 
 class AssetLibraryAdapter(PropertyGroup):
@@ -26,7 +28,7 @@ class AssetLibraryAdapter(PropertyGroup):
     name = "Base Adapter"
     #library = None
 
-    bundle_directory : StringProperty()
+    #bundle_directory : StringProperty()
     
     @property
     def library(self):
@@ -37,29 +39,9 @@ class AssetLibraryAdapter(PropertyGroup):
             if lib.conform.adapter == self:
                 return lib
 
-    @property
-    def library_path(self):
-        return self.library.library_path
-
-    @property
-    def image_template(self):
-        return Template(self.library.image_template)
-
-    @property
-    def video_template(self):
-        return Template(self.library.video_template)
-
-    @property
-    def asset_description_template(self):
-        return Template(self.library.asset_description_template)
-
-    @property
-    def data_type(self):
-        return self.library.data_type
-
-    @property
-    def data_types(self):
-        return self.library.data_types
+    #@property
+    #def library_path(self):
+    #    return self.library.library_path
 
     @property
     def is_conform(self):
@@ -70,29 +52,70 @@ class AssetLibraryAdapter(PropertyGroup):
             if lib.conform.adapter == self:
                 return True 
 
+    @property
+    def target_directory(self):
+        if self.is_conform:
+            return self.library.conform.directory
+
+        return self.library.bundle_dir
+    
     @property
     def blend_depth(self):
         if self.is_conform:
             return self.library.conform.blend_depth
 
         return self.library.blend_depth
+    
+    @property
+    def template_image(self):
+        return Template(self.library.conform.template_image)
 
     @property
-    def externalize_data(self):
-        return self.library.externalize_data
+    def template_video(self):
+        return Template(self.library.conform.template_video)
 
     @property
-    def catalog_path(self):
-        return self.library.catalog_path
+    def template_description(self):
+        return Template(self.library.conform.template_description)
+    
 
-    def get_catalog_path(self, filepath):
-        return get_catalog_path(filepath)
+    @property
+    def data_type(self):
+        return self.library.data_type
+
+    @property
+    def data_types(self):
+        return self.library.data_types
+
+    #@property
+    #def externalize_data(self):
+    #    return self.library.externalize_data
+
+    #@property
+    #def catalog_path(self):
+    #    return self.library.catalog_path
+
+    def get_catalog_path(self, directory=None):
+        directory = directory or self.target_directory
+        return Path(directory, 'blender_assets.cats.txt')
 
     @property
     def cache_file(self):
-        return Path(self.library_path) / f"blender_assets.{self.library.id}.json"
+        return Path(self.target_directory) / f"blender_assets.{self.library.id}.json"
         #return get_asset_datas_file(self.library_path)
 
+    @property
+    def diff_file(self):
+        return Path(bpy.app.tempdir, 'diff.json')
+
+    @property
+    def preview_blend(self):
+        return MODULE_DIR / self.data_type.lower() / "preview.blend"
+
+    @property
+    def preview_assets_file(self):
+        return Path(bpy.app.tempdir, "preview_assets_file.json")
+
     @property
     def addon_prefs(self):
         return get_addon_prefs()
@@ -116,6 +139,12 @@ class AssetLibraryAdapter(PropertyGroup):
     def norm_file_name(self, name):
         return name.replace(' ', '_')
 
+    def read_file(self, file):
+        return read_file(file)
+
+    def write_file(self, file, data):
+        return write_file(file, data)
+
     def copy_file(self, source, destination):
         src = Path(source)
         dst = Path(destination)
@@ -185,6 +214,31 @@ class AssetLibraryAdapter(PropertyGroup):
 
         return asset_path
 
+    def get_template_path(self, template, name, asset_path, catalog):
+        
+        if template.startswith('.'): #the template is relative
+            template = Path(asset_path, template).as_posix()
+
+        params = {
+            'name': name,
+            'asset_path': Path(asset_path),
+            'catalog': catalog,
+            'catalog_name': catalog.replace('/', '_'),
+        }
+
+        return self.format_path(template, **params)
+
+    def get_description_path(self, name, asset_path, catalog) -> Path:
+        """"Get the path of the json or yaml describing all assets data in one file"""
+        return self.get_template_path(self.library.conform.template_description, name, asset_path, catalog)
+
+    def get_image_path(self, name, asset_path, catalog) -> Path:
+        return self.get_template_path(self.library.conform.template_image, name, asset_path, catalog)
+
+    def get_video_path(self, name, asset_path, catalog) -> Path:
+        return self.get_template_path(self.library.conform.template_video, name, asset_path, catalog)
+
+    '''
     def get_path(self, type, name, asset_path, template=None) -> Path:
         if not template:
             template = getattr(self, f'{type}_template')
@@ -193,27 +247,40 @@ class AssetLibraryAdapter(PropertyGroup):
             template = Template(template)
 
         filepath = Path(asset_path)
-        return (filepath / template.format(name=name, path=Path(asset_path))).resolve()
+
+        params = {
+            'bundle_dir': self.library.bundle_directory,
+            'conform_dir': self.library.conform.directory,
+            'rel_path': '',
+            'catalog':'',
+            'catalog_name':'',
+            'name': name
+        }
+
+        return self.format_path(template, params)#(filepath / template.format(name=name, path=Path(asset_path))).resolve()
 
     #def get_image_path(self, name, asset_path):
     #    filepath = Path(asset_path)
     #    image_name = self._get_file_name(name, asset_path)
-    #    return (filepath / self.image_template.format(name=image_name)).resolve()
+    #    return (filepath / self.template_image.format(name=image_name)).resolve()
 
+    
     def get_cache_image_path(self, name, catalog) -> Path:
         """"Get the the cache path of a image for asset without an externalized image"""
+        name = self.norm_file_name(name)
         return Path(self.library_path, '.previews', f"{catalog.replace('/', '_')}_{name}").with_suffix(('.png'))
 
     def get_cache_image(self, name, catalog):
         cache_image_path = self.get_cache_image_path(name, catalog)
         if cache_image_path.exists():
             return cache_image_path
+    '''
 
     #def get_video_path(self, name, asset_path):
     #    filepath = Path(asset_path)
     #    video_name = self._get_file_name(name, asset_path)
-    #    return (filepath / self.video_template.format(name=video_name)).resolve()
-
+    #    return (filepath / self.template_video.format(name=video_name)).resolve()
+    '''
     def get_image(self, name, asset_path):
         image_path = self.get_path('image', name, asset_path)
         if image_path.exists():
@@ -223,21 +290,19 @@ class AssetLibraryAdapter(PropertyGroup):
         video_path = self.get_path('video', name, asset_path)
         if video_path.exists():
             return video_path
+            '''
 
-    def get_asset_description_path(self, asset_path) -> Path:
-        """"Get the path of the json or yaml describing all assets data in onle file"""
-        filepath = Path(asset_path)
-        return (filepath / self.asset_description_template.format(name=filepath.stem)).resolve()
 
-    def read_asset_description(self, asset_path) -> dict:
+
+    def read_asset_description_file(self, asset_path) -> dict:
         """Read the description file of the asset"""
 
-        asset_description_path = self.get_asset_description_path(asset_path)
-        return read_file(asset_description_path)
+        description_path = self.get_description_path(asset_path)
+        return self.read_file(description_path)
 
-    def write_asset_description(self, asset_data, asset_path) -> None:
-        asset_description_path = self.get_asset_description_path(asset_path)
-        return write_file(asset_description_path, asset_data)
+    def write_description_file(self, asset_data, asset_path) -> None:
+        description_path = self.get_description_path(asset_path)
+        return write_file(description_path, asset_data)
 
     def write_asset(self, asset, asset_path):
         bpy.data.libraries.write(
@@ -247,27 +312,48 @@ class AssetLibraryAdapter(PropertyGroup):
             fake_user=True,
             compress=True
         )
-
     
-    def read_catalog(self, filepath=None):
-        """Read the catalog file of the library bundle path or of the specified filepath"""
+    def read_catalog(self, directory=None):
+        """Read the catalog file of the library target directory or of the specified directory"""
+        catalog_path = self.get_catalog_path(directory)
 
-        catalog_path = self.catalog_path
-        if filepath:
-            catalog_path = self.get_catalog_path(filepath)
-        return read_catalog(catalog_path)
+        cat_data = {}
 
-    def write_catalog(self, catalog_data, filepath=None):
-        """Write the catalog file in the library bundle path or of the specified filepath"""
+        for line in catalog_path.read_text(encoding="utf-8").split('\n'):
+            if line.startswith(('VERSION', '#')) or not line:
+                continue
+
+            cat_id, cat_path, cat_name = line.split(':')
+            cat_data[cat_path] = {'id':cat_id, 'name':cat_name}
         
-        catalog_path = self.catalog_path
-        if filepath:
-            catalog_path = self.get_catalog_path(filepath)
+        return cat_data
+
+    def write_catalog(self, catalog_data, directory=None):
+        """Write the catalog file in the library target directory or of the specified directory"""
         
-        return write_catalog(catalog_path, catalog_data)
+        catalog_path = self.get_catalog_path(directory)
+
+        lines = ['VERSION 1', '']
+
+        # Add missing parents catalog
+        norm_data = {}
+        for cat_path, cat_data in catalog_data.items():
+            norm_data[cat_path] = cat_data
+            for p in Path(cat_path).parents[:-1]:
+                if p in data or p in norm_data:
+                    continue
+                
+                norm_data[p.as_posix()] = {'id': str(uuid.uuid4()), 'name': '-'.join(p.parts)}
+
+        for cat_path, cat_data in sorted(norm_data.items()):
+            cat_name = cat_data['name'].replace('/', '-')
+            lines.append(f"{cat_data['id']}:{cat_path}:{cat_name}")
+        
+        print(f'Catalog writen at: {catalog_path}')
+        catalog_path.write_text('\n'.join(lines), encoding="utf-8")
 
     def read_cache(self):
-        return read_file(self.cache_file)
+        return self.read_file(self.cache_file)
 
     def norm_asset_datas(self, asset_file_datas):
         ''' Return a new flat list of asset data
@@ -326,8 +412,148 @@ class AssetLibraryAdapter(PropertyGroup):
 
         return catalog_parts[:self.blend_depth]
 
+    #def transfert_preview(self, )
+
+    '''
+    def generate_previews(self, assets, callback):
+        def _generate_previews(assets, callback, src_assets=None):
+            if src_assets:
+                src_assets = []
+
+            if bpy.app.is_job_running('RENDER_PREVIEW'):
+                print("Waiting for render...")
+                return 0.2  # waiting time
+            
+            while assets:  # generate next preview
+                asset = assets.pop()                
+                #print(f"Creating preview for world {world.name}...")
+                
+                asset_path = asset.asset_data['filepath']
+                src_asset = self.load_datablocks(asset_path, names=asset.name, link=False, type=self.data_types)
+                if not src_asset:
+                    #print(f'No asset named {asset.name} in {asset_path]}')
+                    return
+
+                src_assets.append(src_asset)
+                # # set image in the preview object's material
+                # obj = bpy.context.active_object
+                # image = world.node_tree.nodes['Environment Texture'].image
+                # obj.material_slots[0].material.node_tree.nodes['Image Texture'].image = image
+                if self.data_type == 'COLLECTION':
+                    asset.children.link(src_asset)
+
+                # start preview render
+                with bpy.context.temp_override(id=asset):
+                    bpy.ops.ed.lib_id_generate_preview()
+                return 0.2
+            
+            for asset in src_asset:
+                asset.user_clear()
+            bpy.ops.outliner.orphans_purge(do_local_ids=True, do_linked_ids=True, do_recursive=True)
+
+            callback()
+            return None
+
+    assets = assets.copy()
+    
+    # create preview images
+    bpy.app.timers.register(
+        functools.partial(
+            _generate_previews, 
+            assets, 
+            callback
+        )
+    )
+    '''
+    def generate_preview(self, asset_description):
+        """Only generate preview when conforming a library"""
+
+        #print('generate_preview', filepath, asset_names, data_type)
+
+        scn = bpy.context.scene
+        #Creating the preview for collection, object or material
+        camera = scn.camera
+        vl = bpy.context.view_layer
+
+        data_type = self.data_type #asset_description['data_type']
+        asset_path = asset_description['filepath']
+        asset_data_names = {}
+        for asset_data in asset_description['assets']:
+
+            name = asset_data['name']
+            catalog = asset_data['catalog']
+
+            image_path = self.get_image_path(name, asset_path, catalog)
+            if image_path.exists():
+                continue
+            
+            #Store in a dict all asset_data that does not have preview
+            asset_data_names[name] = dict(asset_data, image_path=image_path)
+        
+        if not asset_data_names:
+            # No preview to generate
+            return
+
+        asset_names = list(asset_data_names.keys())
+        assets = self.load_datablocks(asset_path, names=asset_names, link=True, type=data_type)
+
+        for asset in assets:
+            if not asset:
+                continue
+
+            asset_data = asset_data_names[asset.name]
+            image_path = asset_data['image_path']
+            if data_type == 'COLLECTION':
+
+                bpy.ops.object.collection_instance_add(name=asset.name)
+                
+                bpy.ops.view3d.camera_to_view_selected()
+                instance = vl.objects.active
+
+                #scn.collection.children.link(asset)
+                
+                scn.render.filepath = str(image_path)
+
+
+
+                print(f'Render asset {asset.name} to {image_path}')
+                bpy.ops.render.render(write_still=True)
+
+                #instance.user_clear()
+                asset.user_clear()
+
+                bpy.data.objects.remove(instance)
+
+                #bpy.ops.object.delete(use_global=False)
+
+                #scn.collection.children.unlink(asset)
+
+                bpy.ops.outliner.orphans_purge(do_local_ids=True, do_linked_ids=True, do_recursive=True)
+
+    def generate_previews(self):
+        cache = self.fetch()
+
+        #cache_diff.sort(key=lambda x :x['filepath'])
+        #blend_groups = groupby(cache_diff, key=lambda x :x['filepath'])
+
+        #TODO Support all multiple data_type
+        for asset_description in cache:
+            self.generate_preview(asset_description)
+
+            # filepath = asset_description['filepath']
+
+            # asset_datas = asset_description["assets"]
+
+            # asset_datas.sort(key=lambda x :x.get('type', self.data_type))
+            # data_type_groups = groupby(asset_datas, key=lambda x :x.get('type', self.data_type))
+
+            # for data_type, same_type_asset_datas in data_type_groups:
+                
+            #     asset_names = [a['name'] for a in same_type_asset_datas]
+            #     self.generate_preview(filepath, asset_names, data_type)
+    
     def set_asset_preview(self, asset, asset_data):
-        """Load an externalize image as preview for an asset"""
+        '''Load an externalize image as preview for an asset'''
 
         image_path = Path(asset_data['image'])
         if not image_path.is_absolute():
@@ -339,34 +565,52 @@ class AssetLibraryAdapter(PropertyGroup):
                 bpy.ops.ed.lib_id_load_custom_preview(
                     filepath=str(image_path)
                 )
-            return
         
         if asset.preview:
-            return
-        
+            return asset.preview
+            
+        return
+
         #Creating the preview for collection, object or material
         src_asset = self.load_datablocks(asset_data['filepath'], names=asset_data['name'], link=False, type=self.data_types)
         if not src_asset:
             print(f'No asset named {asset_data["name"]} in {asset_data["filepath"]}')
             return
 
-        bpy.ops.ed.lib_id_generate_preview({"id": src_asset})
-        #time.sleep(0.01)
+        if not self.data_type == 'COLLECTION':
+            print(f'Generate preview of type {self.data_type} not supported yet')
+            return
 
-        #Transfering pixels between previews
-        w, h = src_asset.preview.image_size
-        pixels = [0] * (w*h*4)
-        src_asset.preview.image_pixels_float.foreach_get(pixels)
+        # asset.children.link(src_asset)
+        # bpy.ops.ed.lib_id_generate_preview({"id": asset})
 
-        asset.preview_ensure()
-        asset.preview.image_size = src_asset.preview.image_size
-        asset.preview.image_pixels_float.foreach_set(pixels)
+        # while bpy.app.is_job_running("RENDER_PREVIEW"):
+        #     print(bpy.app.is_job_running("RENDER_PREVIEW"))
+        #     time.sleep(0.2)
+
+        # getattr(bpy.data, self.data_types).remove(src_asset)
+        # return asset.preview
+        #src_asset.user_clear()
+        #return src_asset
+
+        #asset.children.unlink(src_asset)
+        #getattr(bpy.data, self.data_types).remove(src_asset)
+        # time.sleep(1)
+
+
+        # #Transfering pixels between previews
+        # w, h = src_asset.preview.image_size
+        # pixels = [0] * (w*h*4)
+        # src_asset.preview.image_pixels_float.foreach_get(pixels)
+
+        # asset.preview_ensure()
+        # asset.preview.image_size = src_asset.preview.image_size
+        # asset.preview.image_pixels_float.foreach_set(pixels)
 
         #print('pixels transfered')
 
-        bpy.app.timers.register(partial(getattr(bpy.data, self.data_types).remove, src_asset), first_interval=1)
-
-        #getattr(bpy.data, self.data_types).remove(src_asset)
+        #bpy.app.timers.register(partial(getattr(bpy.data, self.data_types).remove, src_asset), first_interval=1)
+    
 
 
     def set_asset_catalog(self, asset, asset_data, catalog_data):
@@ -405,6 +649,10 @@ class AssetLibraryAdapter(PropertyGroup):
                     continue
                 asset.asset_data.tags.new(tag, skip_if_exists=True)
 
+    def set_asset_description(self, asset, asset_data):
+        """Set asset description base on provided data"""
+        asset.asset_data.description = asset_data.get('description', '')
+
     def bundle(self, cache_diff=None):
         """Group all new assets in one or multiple blends for the asset browser"""
 
@@ -412,7 +660,9 @@ class AssetLibraryAdapter(PropertyGroup):
             print(f'{self.data_type} is not supported yet')
             return
 
-        lib_path = self.library_path
+        target_dir = self.target_directory
+
+
         catalog_data = self.read_catalog() #TODO remove unused catalog
 
         write_cache = False
@@ -423,11 +673,18 @@ class AssetLibraryAdapter(PropertyGroup):
             # Only write complete cache at the end
             write_cache = True
 
+            self.generate_previews()
+
         elif isinstance(cache_diff, (Path, str)):
             cache_diff = json.loads(Path(cache_diff).read_text(encoding='utf-8'))
 
+
+        
+
+
         if self.blend_depth == 0:
-            groups = [(cache_diff)]
+            raise Exception('Blender depth must be 1 at min')
+            #groups = [(cache_diff)]
         else:
             cache_diff.sort(key=self.group_key)
             groups = groupby(cache_diff, key=self.group_key)
@@ -440,9 +697,10 @@ class AssetLibraryAdapter(PropertyGroup):
             return
 
         i = 0
+        #assets_to_preview = []
         for sub_path, asset_datas in groups:
             blend_name = sub_path[-1].replace(' ', '_').lower()
-            blend_path = Path(lib_path, *sub_path, blend_name).with_suffix('.blend')
+            blend_path = Path(target_dir, *sub_path, blend_name).with_suffix('.blend')
 
             if blend_path.exists():
                 print(f'Opening existing bundle blend: {blend_path}')
@@ -471,9 +729,10 @@ class AssetLibraryAdapter(PropertyGroup):
                 elif operation == 'ADD' or not asset:
                     if asset:
                         #raise Exception(f"Asset {asset_data['name']} Already in Blend")
+                        print(f"Asset {asset_data['name']} Already in Blend")
                         getattr(bpy.data, self.data_types).remove(asset)
 
-                    #print(f"INFO: Add new asset: {asset_data['name']}")
+                    print(f"INFO: Add new asset: {asset_data['name']}")
                     asset = getattr(bpy.data, self.data_types).new(name=asset_data['name'])
                 else:
                     print(f'operation {operation} not supported should be in (ADD, REMOVE, MODIFIED)')
@@ -482,26 +741,36 @@ class AssetLibraryAdapter(PropertyGroup):
                 asset.asset_mark()
 
                 self.set_asset_preview(asset, asset_data)
+
+                #if not asset_preview:
+                #    assets_to_preview.append((asset_data['filepath'], asset_data['name'], asset_data['data_type']))
                 #if self.externalize_data:
                 #    self.write_preview(preview, filepath)
 
                 self.set_asset_catalog(asset, asset_data, catalog_data)
                 self.set_asset_metadata(asset, asset_data)
                 self.set_asset_tags(asset, asset_data)
-                asset.asset_data.description = asset_data.get('description', '')
+                self.set_asset_description(asset, asset_data)
+                
 
                 i += 1
 
+            #self.write_asset_preview_file()
+
+            
+
             print(f'Saving Blend to {blend_path}')
 
-            blend_path.parent.mkdir(exist_ok=True, parents=True)
-            bpy.ops.wm.save_as_mainfile(filepath=str(blend_path), compress=True)
+            #blend_path.parent.mkdir(exist_ok=True, parents=True)
+
+            #bpy.ops.wm.save_as_mainfile(filepath=str(blend_path), compress=True)
         
         #if write_cache:
         #    self.write_cache(cache)
 
-        #self.write_catalog(catalog_data)
+        self.write_catalog(catalog_data)
 
+        
         bpy.ops.wm.quit_blender()
     
     def norm_cache(self, cache):
@@ -566,4 +835,11 @@ class AssetLibraryAdapter(PropertyGroup):
             layout.prop(self, k, text=bpy.path.display_name(k))
     
     def format_path(self, template, **kargs):
-        return Template(template).format(self.to_dict(), **kargs).resolve()
\ No newline at end of file
+
+        params = dict(self.to_dict(), 
+            bundle_dir=Path(self.library.bundle_directory),
+            conform_dir=Path(self.library.conform.directory),
+            **kargs
+        )
+
+        return Template(template).format(params).resolve()
\ No newline at end of file
diff --git a/adapters/kitsu.py b/adapters/kitsu.py
index f07e558..1676b59 100644
--- a/adapters/kitsu.py
+++ b/adapters/kitsu.py
@@ -82,8 +82,8 @@ class KitsuLibrary(AssetLibraryAdapter):
                 description=data['description'],
                 tags=[],
                 type=self.data_type,
-                image=str(self.image_template.format(name=asset_name)),
-                video=str(self.video_template.format(name=asset_name)),
+                image=str(self.template_image.format(name=asset_name)),
+                video=str(self.template_video.format(name=asset_name)),
                 name=data['name'])
             ]
         )
@@ -98,17 +98,12 @@ class KitsuLibrary(AssetLibraryAdapter):
     def get_preview(self, asset_data):
 
         name = asset_data['name']
-        preview = (f / image_template.format(name=name)).resolve()
+        preview = (f / template_image.format(name=name)).resolve()
         if not preview.exists():
             preview_blend_file(f, preview)
         
         return preview
 
-    def conform(self, directory, templates):
-        """Split each assets per blend and externalize preview"""
-
-        print(f'Conforming {self.library.name} to {directory}')
-
         
     def fetch(self):
         """Gather in a list all assets found in the folder"""
diff --git a/adapters/scan_folder.py b/adapters/scan_folder.py
index 33afeef..3e2351d 100644
--- a/adapters/scan_folder.py
+++ b/adapters/scan_folder.py
@@ -55,8 +55,8 @@ class ScanFolderLibrary(AssetLibraryAdapter):
             metadata=dict(asset.asset_data),
             tags=asset.asset_data.tags.keys(),
             type=self.data_type,
-            image=str(self.image_template.format(name=asset_name)),
-            video=str(self.video_template.format(name=asset_name)),
+            image=str(self.template_image.format(name=asset_name)),
+            video=str(self.template_video.format(name=asset_name)),
             name=asset.name)
         )
         
@@ -178,7 +178,7 @@ class ScanFolderLibrary(AssetLibraryAdapter):
                 asset.asset_mark()
 
                 # Load external preview if exists
-                #image_template = Template(asset_data['preview'])
+                #template_image = Template(asset_data['preview'])
                 image_path = Path(asset_data['image'])
                 if not image_path.is_absolute():
                     image_path = Path(asset_data['filepath'], image_path)
@@ -242,7 +242,7 @@ class ScanFolderLibrary(AssetLibraryAdapter):
     def get_preview(self, asset_data):
 
         name = asset_data['name']
-        preview = (f / image_template.format(name=name)).resolve()
+        preview = (f / template_image.format(name=name)).resolve()
         if not preview.exists():
             preview_blend_file(f, preview)
         
@@ -264,8 +264,8 @@ class ScanFolderLibrary(AssetLibraryAdapter):
         catalog_ids = {v['id']: {'path': k, 'name': v['name']} for k,v in catalog_data.items()}
         directory = Path(directory).resolve()
 
-        image_template = templates.get('image') or self.image_template
-        video_template = templates.get('video') or self.video_template
+        template_image = templates.get('image') or self.template_image
+        template_video = templates.get('video') or self.template_video
 
         # Get list of all modifications
         for blend_file in self._find_blend_files():
@@ -295,12 +295,12 @@ class ScanFolderLibrary(AssetLibraryAdapter):
                 asset_path = self.get_asset_path(name=asset.name, catalog=catalog_path, directory=directory)
                 asset_description = self.get_asset_description(asset, catalog=catalog_path, modified=modified)
 
-                self.write_asset_description(asset_description, asset_path)
+                self.write_description_file(asset_description, asset_path)
                 #Write blend file containing only one asset
                 self.write_asset(asset=asset, asset_path=asset_path)
 
                 # Copy image if source image found else write the asset preview
-                src_image_path = self.get_path('image', name=asset.name, asset_path=blend_file, template=image_template)
+                src_image_path = self.get_path('image', name=asset.name, asset_path=blend_file, template=template_image)
                 dst_image_path = self.get_path('image', name=asset.name, asset_path=asset_path)
 
                 if src_image_path.exists():
@@ -309,7 +309,7 @@ class ScanFolderLibrary(AssetLibraryAdapter):
                     self.write_preview(asset.preview, dst_image_path)
 
                 # Copy video if source video found
-                src_video_path = self.get_path('video', name=asset.name, asset_path=blend_file, template=video_template)
+                src_video_path = self.get_path('video', name=asset.name, asset_path=blend_file, template=template_video)
 
                 #print('src_video_path', src_video_path)
                 if src_video_path.exists():
@@ -364,7 +364,7 @@ class ScanFolderLibrary(AssetLibraryAdapter):
             if not field_data:
                 raise Exception()
 
-            #asset_data = (blend_file / prefs.asset_description_template.format(name=name)).resolve()
+            #asset_data = (blend_file / prefs.template_description.format(name=name)).resolve()
 
             catalogs = [v for k,v in sorted(field_data.items()) if k.isdigit()]
             catalogs = [c.replace('_', ' ').title() for c in catalogs]
@@ -387,7 +387,7 @@ class ScanFolderLibrary(AssetLibraryAdapter):
                 continue
 
             #First Check if there is a asset_data .json
-            asset_description = self.read_asset_description(blend_file)
+            asset_description = self.read_asset_description_file(blend_file)
 
             if not asset_description:
                 # Scan the blend file for assets inside and write a custom asset description for info found
diff --git a/collection/preview.blend b/collection/preview.blend
new file mode 100644
index 0000000..2ca4d64
Binary files /dev/null and b/collection/preview.blend differ
diff --git a/common/bl_utils.py b/common/bl_utils.py
index edac2c5..5fa190b 100644
--- a/common/bl_utils.py
+++ b/common/bl_utils.py
@@ -332,6 +332,9 @@ def load_datablocks(src, names=None, type='objects', link=True, expr=None) -> li
     return_list = not isinstance(names, str)
     names = names or []
 
+    if type.isupper():
+        type = f'{type.lower()}s'
+
     if not isinstance(names, (list, tuple)):
         names = [names]
     
diff --git a/common/file_utils.py b/common/file_utils.py
index e0e93b5..3286202 100644
--- a/common/file_utils.py
+++ b/common/file_utils.py
@@ -13,6 +13,17 @@ import importlib
 import sys
 import shutil
 
+import contextlib
+
+@contextlib.contextmanager
+def cd(path):
+    """Changes working directory and returns to previous on exit."""
+    prev_cwd = Path.cwd()
+    os.chdir(path)
+    try:
+        yield
+    finally:
+        os.chdir(prev_cwd)
 
 def install_module(module_name, package_name=None):
     '''Install a python module with pip or return it if already installed'''
diff --git a/common/functions.py b/common/functions.py
index 952cdeb..2163b41 100644
--- a/common/functions.py
+++ b/common/functions.py
@@ -181,6 +181,7 @@ def get_asset_source(replace_local=False):
 
     return source_path
 
+'''
 def get_catalog_path(filepath=None):
     filepath = filepath or bpy.data.filepath
     filepath = Path(filepath)
@@ -195,7 +196,7 @@ def get_catalog_path(filepath=None):
         catalog.touch(exist_ok=False)
 
     return catalog
-
+'''
 
 # def read_catalog(path, key='path'):
 #     cat_data = {}
@@ -219,7 +220,7 @@ def get_catalog_path(filepath=None):
 #             cat_data[cat_name] = {'id':cat_id, 'path':cat_path}
     
 #     return cat_data
-
+"""
 def read_catalog(path):
     cat_data = {}
 
@@ -299,6 +300,7 @@ def create_catalog_file(json_path : str|Path, keep_existing_category : bool = Tr
     print(f'Catalog saved at: {catalog_path}')
 
     return 
+"""
 
 def clear_env_libraries():
     print('clear_env_libraries')
diff --git a/common/template.py b/common/template.py
index a7d9230..f57065f 100644
--- a/common/template.py
+++ b/common/template.py
@@ -54,14 +54,12 @@ class Template:
 
     def format(self, data=None, **kargs):
 
-        #print('format', self.template, data, kargs)
-
         data = {**(data or {}), **kargs}
 
         try:
             path = self.template.format(**data)
-        except KeyError: 
-            print(f'Cannot format {self.template} with {data}')
+        except KeyError as e:
+            print(f'Cannot format {self.template} with {data}, field {e} is missing')
             return
 
         path = os.path.expandvars(path)
diff --git a/constants.py b/constants.py
index f00f20e..df7b508 100644
--- a/constants.py
+++ b/constants.py
@@ -13,4 +13,5 @@ ASSETLIB_FILENAME = "blender_assets.libs.json"
 MODULE_DIR = Path(__file__).parent
 RESOURCES_DIR = MODULE_DIR / 'resources'
 ADAPTER_DIR = MODULE_DIR / 'adapters'
-ADAPTERS = []
\ No newline at end of file
+ADAPTERS = []
+PREVIEW_ASSETS_SCRIPT = MODULE_DIR / 'common' / 'preview_assets.py'
diff --git a/file/bundle.py b/file/bundle.py
index f4e2da7..2e5e440 100644
--- a/file/bundle.py
+++ b/file/bundle.py
@@ -17,7 +17,7 @@ command, write_catalog)
 
 
 @command
-def bundle_library(source_directory, bundle_directory, asset_description_template, thumbnail_template, 
+def bundle_library(source_directory, bundle_directory, template_description, thumbnail_template, 
         template=None, data_file=None):
 
     field_pattern = r'{(\w+)}'
@@ -38,7 +38,7 @@ def bundle_library(source_directory, bundle_directory, asset_description_templat
 
         name = field_data.get('name', f.stem)
         thumbnail = (f / thumbnail_template.format(name=name)).resolve()
-        asset_data = (f / asset_description_template.format(name=name)).resolve()
+        asset_data = (f / template_description.format(name=name)).resolve()
 
         catalogs = sorted([v for k,v in sorted(field_data.items()) if k.isdigit()])
         catalogs = [c.replace('_', ' ').title() for c in catalogs]
@@ -163,7 +163,7 @@ if __name__ == '__main__' :
     bundle_library(
         source_directory=args.source_directory,
         bundle_directory=args.bundle_directory,
-        asset_description_template=args.asset_description_template,
+        template_description=args.template_description,
         thumbnail_template=args.thumbnail_template,
         template=args.template,
         data_file=args.data_file)
diff --git a/operators.py b/operators.py
index 2fb20a1..62cf8b9 100644
--- a/operators.py
+++ b/operators.py
@@ -112,8 +112,8 @@ class ASSETLIB_OT_edit_data(Operator):
             new_video_path = lib.adapter.get_path('video', new_name, new_asset_path)
             self.old_video_path.rename(new_video_path)
 
-        if self.old_asset_description_path.exists():
-            self.old_asset_description_path.unlink()
+        if self.old_description_path.exists():
+            self.old_description_path.unlink()
 
         new_asset_description = lib.adapter.get_asset_description(
             asset=self.asset,
@@ -121,7 +121,7 @@ class ASSETLIB_OT_edit_data(Operator):
             modified=time.time_ns()
         )
 
-        lib.adapter.write_asset_description(new_asset_description, new_asset_path)
+        lib.adapter.write_description_file(new_asset_description, new_asset_path)
 
         if not list(self.old_asset_path.parent.iterdir()):
             self.old_asset_path.parent.rmdir()
@@ -187,9 +187,9 @@ class ASSETLIB_OT_edit_data(Operator):
         self.old_image_path = lib.adapter.get_path('image', self.old_asset_name, self.old_asset_path)
         self.old_video_path = lib.adapter.get_path('video', self.old_asset_name, self.old_asset_path)
 
-        self.old_asset_description_path = lib.adapter.get_asset_description_path(self.old_asset_path)
+        self.old_description_path = lib.adapter.get_description_path(self.old_asset_path)
         
-        self.old_asset_description = lib.adapter.read_asset_description(self.old_asset_path)
+        self.old_asset_description = lib.adapter.read_asset_description_file(self.old_asset_path)
         self.old_asset_description = lib.adapter.norm_asset_datas([self.old_asset_description])[0]
 
 
@@ -408,8 +408,8 @@ class ASSETLIB_OT_conform_library(Operator):
     bl_description = "Split each assets per blend and externalize preview"
 
     name : StringProperty()
-    image_template : StringProperty()
-    video_template : StringProperty()
+    template_image : StringProperty()
+    template_video : StringProperty()
     directory : StringProperty(subtype='DIR_PATH', name='Filepath')
 
     def execute(self, context: Context) -> Set[str]:
@@ -419,13 +419,13 @@ class ASSETLIB_OT_conform_library(Operator):
         #lib.adapter.conform(self.directory)
 
         templates = {}
-        if self.image_template:
-            templates['image'] = self.image_template
-        if self.video_template:
-            templates['video'] = self.video_template
+        if self.template_image:
+            templates['image'] = self.template_image
+        if self.template_video:
+            templates['video'] = self.template_video
 
 
-        script_path = Path(gettempdir()) / 'bundle_library.py'
+        script_path = Path(bpy.app.tempdir) / 'bundle_library.py'
         script_code = dedent(f"""
             import bpy
             prefs = bpy.context.preferences.addons["asset_library"].preferences
@@ -447,6 +447,58 @@ class ASSETLIB_OT_conform_library(Operator):
         return {'RUNNING_MODAL'}
 
 
+class ASSETLIB_OT_generate_previews(Operator):
+    bl_idname = "assetlib.generate_previews"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_label = "Generate Previews"
+    bl_description = "Generate and write the image for assets"
+
+    diff : StringProperty()
+    preview_blend : StringProperty()
+    name : StringProperty()
+    blocking : BoolProperty(default=True)
+
+    def execute(self, context: Context) -> Set[str]:
+        prefs = get_addon_prefs()
+        lib = prefs.libraries.get(self.name)
+        # self.write_file(self.diff_file, self.diff)
+
+        # preview_assets = [(a.asset_data['filepath'], self.data_types, a.name) for a in assets]
+
+        # self.preview_assets_file.write_text(json.dumps(preview_assets), encoding='utf-8')
+
+        # cmd = [
+        #     bpy.app.binary_path, '-b', '--use-system-env',
+        #     '--python', str(PREVIEW_ASSETS_SCRIPT), '--',
+        #     '--preview-blend', str(self.preview_blend), 
+        #     '--preview-assets-file', str(self.preview_assets_file)
+        # ]
+        # subprocess.call(cmd)
+        preview_blend = self.preview_blend or lib.adapter.preview_blend
+        
+        script_path = Path(bpy.app.tempdir) / 'generate_previews.py'
+        script_code = dedent(f"""
+            import bpy
+            prefs = bpy.context.preferences.addons["asset_library"].preferences
+            lib = prefs.env_libraries.add()
+            lib.set_dict({lib.to_dict()})
+
+            bpy.ops.wm.open_mainfile(filepath='{preview_blend}', load_ui=True)
+            lib.conform.adapter.generate_previews()
+            """)
+
+        script_path.write_text(script_code)
+
+        cmd = get_bl_cmd(script=str(script_path), background=True)
+
+        if self.blocking:
+            subprocess.call(cmd)
+        else:
+            subprocess.Popen(cmd)
+
+
+        return {'FINISHED'}
+
 class ASSETLIB_OT_play_preview(Operator):
     bl_idname = "assetlib.play_preview"
     bl_options = {"REGISTER", "UNDO", "INTERNAL"}
@@ -553,6 +605,7 @@ classes = (
     ASSETLIB_OT_add_user_library,
     ASSETLIB_OT_remove_user_library,
     ASSETLIB_OT_diff,
+    ASSETLIB_OT_generate_previews,
     ASSETLIB_OT_bundle_library,
     ASSETLIB_OT_clear_asset,
     ASSETLIB_OT_edit_data,
diff --git a/prefs.py b/prefs.py
index f806d1f..3dc003a 100644
--- a/prefs.py
+++ b/prefs.py
@@ -12,7 +12,7 @@ from asset_library.constants import (DATA_TYPES, DATA_TYPE_ITEMS,
 
 from asset_library.common.file_utils import import_module_from_path, norm_str
 from asset_library.common.bl_utils import get_addon_prefs
-from asset_library.common.functions import get_catalog_path
+#from asset_library.common.functions import get_catalog_path
 
 from pathlib import Path
 import importlib
@@ -88,14 +88,16 @@ class ConformAssetLibrary(PropertyGroup):
     adapters : bpy.props.PointerProperty(type=AssetLibraryAdapters)
     adapter_name : EnumProperty(items=get_adapter_items)
     directory : StringProperty(
-        name="Destination Directory",
+        name="Target Directory",
         subtype='DIR_PATH',
         default=''
     )
-    image_template : StringProperty()
-    video_template : StringProperty()
 
-    externalize_data: BoolProperty(default=False, name='Externalize Data')
+    template_image : StringProperty(default='', description='../{name}_image.png')
+    template_video : StringProperty(default='', description='../{name}_video.mov')
+    template_description : StringProperty(default='', description='../{name}_asset_description.json')
+    
+    #externalize_data: BoolProperty(default=False, name='Externalize Data')
     blend_depth: IntProperty(default=1, name='Blend Depth')
 
     @property
@@ -228,23 +230,23 @@ class AssetLibrary(PropertyGroup):
         return self.name
 
     @property
-    def image_template(self):
+    def template_image(self):
         prefs = get_addon_prefs()
-        return prefs.image_template
+        return prefs.template_image
 
     @property
-    def video_template(self):
+    def template_video(self):
         prefs = get_addon_prefs()
-        return prefs.video_template
+        return prefs.template_video
 
     @property
-    def asset_description_template(self):
+    def template_description(self):
         prefs = get_addon_prefs()
-        return prefs.asset_description_template
+        return prefs.template_description
 
-    @property
-    def catalog_path(self):
-        return get_catalog_path(self.library_path)
+    #@property
+    #def catalog_path(self):
+    #    return get_catalog_path(self.library_path)
 
     @property
     def options(self):
@@ -376,7 +378,7 @@ class AssetLibrary(PropertyGroup):
         if not self.use:
             if all(not l.use for l in self.merge_libraries):
                 self.clear_library_path()
-                return
+            return
 
         # Create the Asset Library Path
         if not lib:
@@ -470,6 +472,10 @@ class AssetLibrary(PropertyGroup):
         op.name = self.name
         op.conform = True
 
+        op = subrow.operator('assetlib.generate_previews', text='', icon='SEQ_PREVIEW')#, icon='MOD_BUILD'
+        op.name = self.name
+        #op.conform = True
+
         op = subrow.operator('assetlib.bundle', text='', icon='MOD_BUILD')#, icon='MOD_BUILD'
         op.name = self.name
         op.directory = self.conform.directory
@@ -479,17 +485,22 @@ class AssetLibrary(PropertyGroup):
         #subrow.separator(factor=3)
 
         if self.expand_extra and self.conform.adapter:
+            col.separator()
+            self.conform.adapter.draw_prefs(col)    
+
+            col.separator()
             col.separator()
             #row = layout.row(align=True)
             #row.label(text='Conform Library')
             col.prop(self.conform, "directory")
             col.prop(self.conform, "blend_depth")
-            col.prop(self.conform, "externalize_data")
-            col.prop(self.conform, "image_template", text='Image Template')
-            col.prop(self.conform, "video_template", text='Video Template')
+            #col.prop(self.conform, "externalize_data")
+            subcol = col.column(align=True)
+            subcol.prop(self.conform, "template_description", text='Template Description', icon='COPY_ID')
+            subcol.prop(self.conform, "template_image", text='Template Image', icon='COPY_ID')
+            subcol.prop(self.conform, "template_video", text='Template Video', icon='COPY_ID')
 
-            col.separator()
-            self.conform.adapter.draw_prefs(col)              
+                      
 
         col.separator()
 
@@ -651,10 +662,10 @@ class AssetLibraryPrefs(AddonPreferences):
         update=update_all_library_path
     )
 
-    use_single_path : BoolProperty(default=True)
-    asset_description_template : StringProperty(default='../{name}_asset_description.json')
-    image_template : StringProperty(default='../{name}_image.png')
-    video_template : StringProperty(default='../{name}_video.mov')
+    #use_single_path : BoolProperty(default=True)
+    #template_description : StringProperty(default='../{name}_asset_description.json')
+    #template_image : StringProperty(default='../{name}_image.png')
+    #template_video : StringProperty(default='../{name}_video.mov')
 
     config_directory : StringProperty(
         name="Config Path",
@@ -745,16 +756,16 @@ class AssetLibraryPrefs(AddonPreferences):
 
             col.separator()
 
-            col.prop(self, 'asset_description_template', text='Asset Description Template', icon='COPY_ID')
+            #col.prop(self, 'template_description', text='Asset Description Template', icon='COPY_ID')
 
-            col.separator()
+            #col.separator()
 
-            col.prop(self, 'image_template', text='Image Template', icon='COPY_ID')
+            #col.prop(self, 'template_image', text='Template Image', icon='COPY_ID')
             col.prop(self, 'image_player', text='Image Player') #icon='OUTLINER_OB_IMAGE'
 
-            col.separator()
+            #col.separator()
 
-            col.prop(self, 'video_template', text='Video Template', icon='COPY_ID')
+            #col.prop(self, 'template_video', text='Template Video', icon='COPY_ID')
             col.prop(self, 'video_player', text='Video Player') #icon='FILE_MOVIE'
 
             col.separator()