diff --git a/lib/src/call_handlers/offline_call_handler.dart b/lib/src/call_handlers/offline_call_handler.dart
index 3951dab..b20482d 100644
--- a/lib/src/call_handlers/offline_call_handler.dart
+++ b/lib/src/call_handlers/offline_call_handler.dart
@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:http/http.dart' as http;
@@ -82,6 +83,10 @@ class OfflineCallHandler extends CallHandler
     final endpoint = getEndpoint(params);
     final offlinePersistency = getOfflinePersistency(params);
 
+    if (offlinePersistency) {
+      params.headers['X-SDK-Offline'] = 'true';
+    }
+
     while (true) {
       try {
         // if offline, do offline stuff
@@ -96,19 +101,36 @@ class OfflineCallHandler extends CallHandler
 
         final pathValues = routeMatch?.getPathValues(params.path);
 
-        final model = modelPattern.split('/').map((part) {
-          if (!part.startsWith('{') || !part.endsWith('}')) {
-            return part;
+        String replacePlaceholder(
+            String input, Map<String, String>? pathValues) {
+          if (!input.startsWith('{') || !input.endsWith('}')) {
+            return input;
           }
-          return pathValues![part.substring(1, part.length - 1)];
+          return pathValues![input.substring(1, input.length - 1)]!;
+        }
+
+        final model = modelPattern.split('/').map((part) {
+          return replacePlaceholder(part, pathValues);
         }).join('/');
 
+        final keyPattern = routeMatch?.getLabel('offline.key') ?? '';
+        final key = replacePlaceholder(
+          keyPattern,
+          pathValues,
+        );
+
+        final containerKeyPattern =
+            routeMatch?.getLabel('offline.container-key') ?? '';
+        final containerKey = replacePlaceholder(
+          containerKeyPattern,
+          pathValues,
+        );
+
         final cacheParams = CacheParams(
           model: model,
-          key: routeMatch?.getLabel('offline.key') as String,
+          key: key,
           responseIdKey: routeMatch?.getLabel('offline.response-key') as String,
-          responseContainerKey:
-              routeMatch?.getLabel('offline.container-key') as String,
+          responseContainerKey: containerKey,
         );
 
         final uri = Uri.parse(endpoint + params.path);
@@ -145,15 +167,23 @@ class OfflineCallHandler extends CallHandler
 
         final response = await next.handleCall(params);
 
-        // cache stuff
-        print('cached stuff...');
         if (offlinePersistency) {
+          // cache stuff
+          print('cached stuff...');
+
+          final relationsHeader = response.headers['x-appwrite-relations'];
+          if (relationsHeader != null) {
+            final relations = (jsonDecode(relationsHeader) as List)
+                .cast<Map<String, dynamic>>();
+            await cacheCollections(relations);
+          }
           cacheResponse(
             cacheModel: cacheParams.model,
             cacheKey: cacheParams.key,
             cacheResponseIdKey: cacheParams.responseIdKey,
-            request: request,
-            response: response,
+            cacheResponseContainerKey: cacheParams.responseContainerKey,
+            requestMethod: request.method,
+            responseData: response.data,
           );
         }
 
@@ -170,7 +200,8 @@ class OfflineCallHandler extends CallHandler
           rethrow;
         }
         isOnline.value = false;
-      } catch (e) {
+      } catch (e, s) {
+        print(s);
         throw AppwriteException(e.toString());
       }
     }
diff --git a/lib/src/client_io.dart b/lib/src/client_io.dart
index 7f10b48..e4f089c 100644
--- a/lib/src/client_io.dart
+++ b/lib/src/client_io.dart
@@ -374,6 +374,10 @@ class ClientIO extends ClientBase with ClientMixin {
 
   @override
   Future<Response> call(CallParams params) async {
+    while (!_initialized) {
+      await Future.delayed(Duration(milliseconds: 100));
+    }
+
     params.headers.addAll(this._headers!);
     final response = await _handler.handleCall(
       withOfflinePersistency(
diff --git a/lib/src/client_offline_mixin.dart b/lib/src/client_offline_mixin.dart
index 6af7493..7cf5646 100644
--- a/lib/src/client_offline_mixin.dart
+++ b/lib/src/client_offline_mixin.dart
@@ -366,45 +366,122 @@ class ClientOfflineMixin {
     return completer.future;
   }
 
+  void cacheRelated({
+    required Map<String, Object?> document,
+  }) {
+    // iterate over each attribute to see if it's nested data
+    document.entries.forEach((entry) {
+      if (entry.value is Map) {
+        final nestedDocument = entry.value as Map<String, Object?>;
+        final nestedDatabaseId = nestedDocument['\$databaseId'] as String?;
+        final nestedCollectionId = nestedDocument['\$collectionId'] as String?;
+        final nestedDocumentId = nestedDocument['\$id'] as String?;
+        if (nestedDatabaseId == null ||
+            nestedCollectionId == null ||
+            nestedDocumentId == null) return;
+        final nestedModel =
+            "/databases/$nestedDatabaseId/collections/$nestedCollectionId/documents";
+        cacheResponse(
+          cacheModel: nestedModel,
+          cacheKey: nestedDocumentId,
+          cacheResponseIdKey: "\$id",
+          cacheResponseContainerKey: '',
+          requestMethod: 'GET',
+          responseData: entry.value,
+        );
+        document[entry.key] = {
+          '\$id': nestedDocumentId,
+          '\$databaseId': nestedDatabaseId,
+          '\$collectionId': nestedCollectionId,
+        };
+      } else if (entry.value is List &&
+          entry.value != null &&
+          (entry.value as List).isNotEmpty) {
+        final values = (entry.value as List);
+        if (!(values.first is Map<String, Object?>)) return;
+        final nestedDocument = values.first;
+        final nestedDatabaseId = nestedDocument['\$databaseId'] as String?;
+        final nestedCollectionId = nestedDocument['\$collectionId'] as String?;
+        if (nestedDatabaseId == null || nestedCollectionId == null) return;
+        final nestedModel =
+            "/databases/$nestedDatabaseId/collections/$nestedCollectionId/documents";
+        cacheResponse(
+          cacheModel: nestedModel,
+          cacheKey: '',
+          cacheResponseIdKey: "\$id",
+          cacheResponseContainerKey: 'documents',
+          requestMethod: 'GET',
+          responseData: {
+            'documents': entry.value,
+          },
+        );
+        document[entry.key] = values.map((value) {
+          final nestedDocumentId = value['\$id'] as String?;
+          return {
+            '\$id': nestedDocumentId,
+            '\$databaseId': nestedDatabaseId,
+            '\$collectionId': nestedCollectionId,
+          };
+        }).toList();
+      }
+    });
+  }
+
+  Future<void> cacheCollections(List<Map<String, dynamic>> relations) {
+    final futures = <Future>[];
+    for (var collection in relations) {
+      futures.add(_modelData.cacheModel(collection));
+    }
+    return Future.wait(futures);
+  }
+
   void cacheResponse({
     required String cacheModel,
     required String cacheKey,
     required String cacheResponseIdKey,
-    required http.BaseRequest request,
-    required Response response,
+    required String cacheResponseContainerKey,
+    required String requestMethod,
+    required dynamic responseData,
   }) {
     if (cacheModel.isEmpty) return;
 
-    switch (request.method) {
+    switch (requestMethod) {
       case 'GET':
-        final clone = cloneMap(response.data);
+        final clone = cloneMap(responseData);
         if (cacheKey.isNotEmpty) {
+          cacheRelated(document: clone);
           _modelData.upsert(model: cacheModel, data: clone, key: cacheKey);
         } else {
-          clone.forEach((key, value) {
-            if (key == 'total') return;
-            _modelData.batchUpsert(
-              model: cacheModel,
-              dataList: value as List,
-              idKey: cacheResponseIdKey,
-            );
+          final values = clone[cacheResponseContainerKey] as List;
+          values.forEach((value) {
+            cacheRelated(document: value);
           });
+          _modelData.batchUpsert(
+            model: cacheModel,
+            dataList: values,
+            idKey: cacheResponseIdKey,
+          );
         }
         break;
       case 'POST':
       case 'PUT':
       case 'PATCH':
-        Map<String, Object?> clone = cloneMap(response.data);
+        Map<String, Object?> clone = cloneMap(responseData);
         if (cacheKey.isEmpty) {
           cacheKey = clone['\$id'] as String;
         }
         if (cacheModel.endsWith('/prefs')) {
-          clone = response.data['prefs'];
+          clone = responseData['prefs'];
         }
         _modelData.upsert(model: cacheModel, data: clone, key: cacheKey);
         break;
       case 'DELETE':
         if (cacheKey.isNotEmpty) {
+          // _modelData.get(model: cacheModel, key: cacheKey).then((cachedData) {
+          //   if (cachedData == null) {
+          //     return;
+          //   }
+          // });
           _modelData.delete(model: cacheModel, key: cacheKey);
         }
     }
diff --git a/lib/src/offline/route_mapping.dart b/lib/src/offline/route_mapping.dart
index 1a591ef..81784f7 100644
--- a/lib/src/offline/route_mapping.dart
+++ b/lib/src/offline/route_mapping.dart
@@ -36,7 +36,7 @@ final routes = [
     "offline": {
       "model":
           "\/databases\/{databaseId}\/collections\/{collectionId}\/documents",
-      "key": "{documentId}",
+      "key": "",
       "response-key": "\$id",
       "container-key": "",
     },
diff --git a/lib/src/offline/services/cache_size.dart b/lib/src/offline/services/cache_size.dart
index cf1b0c8..0934179 100644
--- a/lib/src/offline/services/cache_size.dart
+++ b/lib/src/offline/services/cache_size.dart
@@ -19,23 +19,33 @@ class CacheSize {
     return encoded;
   }
 
-  Future<void> applyChange(int change) async {
-    if (change == 0) return;
+  Future<int?> applyChange(Transaction txn, int change) async {
+    if (change == 0) return null;
 
     final record = getCacheSizeRecordRef();
-
-    final currentSize = await record.get(_db) ?? 0;
-    await record.put(_db, currentSize + change);
+    final currentSize = await record.get(txn) ?? 0;
+    return await record.put(txn, currentSize + change);
   }
 
   Future<void> update({
-    Map<String, dynamic>? oldData,
+    required RecordRef<String, Map<String, Object?>> recordRef,
+    required Transaction txn,
     Map<String, dynamic>? newData,
   }) async {
+    final oldData = await recordRef.get(txn);
     final oldSize = oldData != null ? encode(oldData).length : 0;
     final newSize = newData != null ? encode(newData).length : 0;
     final change = newSize - oldSize;
-    await applyChange(change);
+    final cacheSize = await applyChange(txn, change);
+
+    if (change != 0) {
+      print([
+        '${recordRef.key}: oldSize: $oldSize',
+        'newSize: $newSize',
+        'change: $change',
+        'cacheSize: $cacheSize',
+      ].join(', '));
+    }
   }
 
   void onChange(void callback(int? currentSize)) {
diff --git a/lib/src/offline/services/model_data.dart b/lib/src/offline/services/model_data.dart
index fbda478..a158278 100644
--- a/lib/src/offline/services/model_data.dart
+++ b/lib/src/offline/services/model_data.dart
@@ -1,5 +1,6 @@
 import 'package:appwrite/src/offline/services/cache_size.dart';
 import 'package:sembast/sembast.dart';
+import 'package:sembast/utils/value_utils.dart';
 
 import '../../../appwrite.dart';
 import 'accessed_at.dart';
@@ -8,6 +9,9 @@ class ModelData {
   final Database _db;
   final AccessedAt _accessedAt;
   final CacheSize _cacheSize;
+  final int maxDepth = 3;
+  final documentModelRegex = RegExp(
+      r'^/databases/([a-zA-Z0-9\-]*)/collections/([a-zA-Z0-9\-]*)/documents$');
 
   ModelData(this._db)
       : _accessedAt = AccessedAt(_db),
@@ -17,15 +21,128 @@ class ModelData {
     return stringMapStoreFactory.store(model);
   }
 
+  Future<void> cacheModel(Map<String, dynamic> collection) {
+    final store = stringMapStoreFactory.store('collections');
+
+    return store
+        .record("${collection['databaseId']}|${collection['collectionId']}")
+        .put(_db, collection);
+  }
+
   Future<Map<String, dynamic>?> get({
     required String model,
     required String key,
+  }) async {
+    final immutableRecord = await _getRecord(model: model, key: key);
+
+    if (immutableRecord == null) return null;
+
+    final record = cloneMap(immutableRecord);
+    await _populateRelated(record, 0);
+
+    return record;
+  }
+
+  Future<Map<String, dynamic>?> _getRecord({
+    required String model,
+    required String key,
   }) async {
     final store = getModelStore(model);
     final recordRef = store.record(key);
     return recordRef.get(_db);
   }
 
+  bool _isNestedDocument(Map<String, dynamic> record) {
+    return record.containsKey('\$databaseId') &&
+        record.containsKey('\$collectionId') &&
+        record.containsKey('\$id');
+  }
+
+  /// Given a record with $databaseId, $collectionId and $id, populate the rest
+  /// of the attributes from the cache and then populate the related records.
+  Future<Map<String, dynamic>?> _populateRecord(
+      Map<String, dynamic>? record, int depth) async {
+    if (record == null) return record;
+
+    if (!_isNestedDocument(record)) return record;
+
+    final databaseId = record['\$databaseId'] as String;
+    final collectionId = record['\$collectionId'] as String;
+    final documentId = record['\$id'] as String;
+
+    final nestedModel =
+        "/databases/$databaseId/collections/$collectionId/documents";
+
+    final cached = await _getRecord(
+      model: nestedModel,
+      key: documentId,
+    );
+
+    if (cached == null) return record;
+
+    record.addAll(cloneMap(cached));
+
+    await _populateRelated(record, depth + 1);
+
+    return record;
+  }
+
+  /// Iterate over every attribute of a record and fetch related records from
+  /// the cache.
+  Future<void> _populateRelated(Map<String, dynamic>? record, int depth) {
+    if (record == null) {
+      return Future.value();
+    }
+
+    // iterate over each attribute and check if it is a relation
+    final futures = <Future>[];
+    for (final attribute in record.entries) {
+      if (attribute.value is Map<String, Object?>) {
+        final map = attribute.value as Map<String, Object?>;
+        if (_isNestedDocument(record)) {
+          if (depth >= maxDepth) {
+            record[attribute.key] = null;
+          } else {
+            final future = _populateRecord(map, depth).then((populated) {
+              record[attribute.key] = populated;
+            });
+
+            futures.add(future);
+          }
+        }
+      } else if (attribute.value is List) {
+        final List list = attribute.value as List;
+        final futureList = <Future<Map<String, dynamic>?>>[];
+        if (list.isEmpty) continue;
+
+        if (depth >= maxDepth &&
+            list.first is Map<String, Object?> &&
+            _isNestedDocument(list.first)) {
+          record[attribute.key] = [];
+          continue;
+        }
+
+        for (final map in list) {
+          if (map is! Map<String, Object?>) {
+            continue;
+          }
+          futureList.add(_populateRecord(map, depth));
+        }
+
+        if (futureList.isEmpty) {
+          continue;
+        }
+
+        final future = Future.wait(futureList).then((populated) {
+          record[attribute.key] = populated;
+        });
+
+        futures.add(future);
+      }
+    }
+    return Future.wait(futures);
+  }
+
   Future<Map<String, dynamic>> list({
     required String model,
     required String cacheResponseContainerKey,
@@ -50,6 +167,7 @@ class ModelData {
                 final List<Filter> equalFilters = [];
                 value.forEach((v) {
                   equalFilters.add(Filter.equals(q.params[0], v));
+                  equalFilters.add(Filter.equals("${q.params[0]}.\$id", v));
                 });
                 filters.add(Filter.or(equalFilters));
               });
@@ -82,6 +200,30 @@ class ModelData {
             filters.add(Filter.matches(q.params[0], r'${q.params[1]}+'));
             break;
 
+          case 'isNull':
+            // TODO: Handle this case.
+            break;
+
+          case 'isNotNull':
+            // TODO: Handle this case.
+            break;
+
+          case 'between':
+            // TODO: Handle this case.
+            break;
+
+          case 'startsWith':
+            // TODO: Handle this case.
+            break;
+
+          case 'endsWith':
+            // TODO: Handle this case.
+            break;
+
+          case 'select':
+            // TODO: Handle this case.
+            break;
+
           case 'orderAsc':
             sortOrders.add(SortOrder(q.params[0] as String));
             break;
@@ -116,19 +258,27 @@ class ModelData {
     final records = await store.find(_db, finder: finder);
     final count = await store.count(_db, filter: filter);
 
+    final list = records.map((record) {
+      // convert to Map<String, dynamic>
+      final map = Map<String, dynamic>();
+      record.value.entries.forEach((entry) {
+        map[entry.key] = entry.value;
+      });
+      return map;
+    }).toList();
+
+    final futures = <Future<Map<String, dynamic>?>>[];
+    for (final record in list) {
+      futures.add(_populateRecord(record, 0));
+    }
+
     final keys = records.map((record) => record.key).toList();
 
     _accessedAt.update(model: store.name, keys: keys);
 
     return {
       'total': count,
-      cacheResponseContainerKey: records.map((record) {
-        final map = Map<String, dynamic>();
-        record.value.entries.forEach((entry) {
-          map[entry.key] = entry.value;
-        });
-        return map;
-      }).toList(),
+      cacheResponseContainerKey: await Future.wait(futures),
     };
   }
 
@@ -137,13 +287,90 @@ class ModelData {
     required Map<String, dynamic> data,
     required String key,
   }) async {
-    final store = getModelStore(model);
+    final match = documentModelRegex.firstMatch(model);
+    if (match?.groupCount == 2) {
+      // data is a document
 
-    final recordRef = store.record(key);
-    final record = await recordRef.get(_db);
-    _cacheSize.update(oldData: record, newData: data);
+      // match starting at 1 since 0 is the full match
+      final databaseId = match!.group(1)!;
+      final collectionId = match.group(2)!;
 
-    final result = await recordRef.put(_db, data, merge: true);
+      final collectionStore = getModelStore('collections');
+      final recordRef = collectionStore.record('$databaseId|$collectionId');
+      final collection = await recordRef.get(_db);
+      final attributes = (collection?['attributes'] ?? <Map<String, Object?>>{})
+          as Map<String, Object?>;
+      for (final attributeEntry in attributes.entries) {
+        final key = attributeEntry.key;
+        final attribute = attributeEntry.value as Map<String, Object?>;
+        final relatedCollection = attribute['relatedCollection'] as String;
+        final relationType = attribute['relationType'] as String;
+        final side = attribute['side'] as String;
+
+        if (!data.containsKey(key)) continue;
+
+        final nestedModel =
+            "/databases/$databaseId/collections/$relatedCollection/documents";
+
+        if (relationType == 'oneToOne' ||
+            (relationType == 'oneToMany' && side == 'child') ||
+            (relationType == 'manyToOne' && side == 'parent')) {
+          // data[key] is a single document
+          String documentId = '';
+          if (data[key] is String) {
+            // data[key] is a document ID
+            documentId = data[key] as String;
+          } else if (data[key] is Map<String, Object?>) {
+            // data[key] is a nested document
+            final related = data[key] as Map<String, Object?>;
+            documentId = (related['\$id'] ?? ID.unique()) as String;
+            await upsert(model: nestedModel, key: documentId, data: related);
+          }
+          data[key] = {
+            '\$databaseId': databaseId,
+            '\$collectionId': relatedCollection,
+            '\$id': documentId
+          };
+        } else {
+          // data[key] is a list of documents
+          final result = <Map<String, Object?>>[];
+          final relatedList = data[key] as List;
+          for (final related in relatedList) {
+            String documentId = '';
+            if (related is String) {
+              // related is a document ID
+              documentId = related;
+            } else if (related is Map<String, Object?>) {
+              // related is a nested document
+              documentId = (related['\$id'] ?? ID.unique()) as String;
+              await upsert(model: nestedModel, key: documentId, data: related);
+            }
+            result.add({
+              '\$databaseId': databaseId,
+              '\$collectionId': relatedCollection,
+              '\$id': documentId
+            });
+          }
+          data[key] = result;
+        }
+      }
+    }
+
+    final result = await _db.transaction((txn) async {
+      final store = getModelStore(model);
+
+      final recordRef = store.record(key);
+      final oldData = await recordRef.get(txn);
+      final oldSize = oldData != null ? _cacheSize.encode(oldData).length : 0;
+
+      final result = await recordRef.put(txn, data, merge: true);
+
+      final newSize = _cacheSize.encode(result).length;
+      final change = newSize - oldSize;
+
+      await _cacheSize.applyChange(txn, change);
+      return result;
+    });
     await _accessedAt.update(model: model, keys: [key]);
     return result;
   }
@@ -167,16 +394,19 @@ class ModelData {
   Future<void> delete({required String model, required String key}) async {
     final store = getModelStore(model);
     RecordSnapshot<String, Map<String, Object?>>? record;
+    final recordRef = store.record(key);
 
-    record = await store.record(key).getSnapshot(_db);
+    record = await recordRef.getSnapshot(_db);
 
     if (record == null) {
       return;
     }
 
-    _cacheSize.update(oldData: record.value);
-
-    await record.ref.delete(_db);
+    await _db.transaction((txn) async {
+      final oldSize = _cacheSize.encode(record!.value).length;
+      await _cacheSize.applyChange(txn, oldSize * -1);
+      await record.ref.delete(_db);
+    });
 
     await _accessedAt.delete(model: model, key: record.key);
   }
diff --git a/lib/src/offline_db_io.dart b/lib/src/offline_db_io.dart
index 61b3642..d6cf548 100644
--- a/lib/src/offline_db_io.dart
+++ b/lib/src/offline_db_io.dart
@@ -3,7 +3,7 @@ import 'dart:io';
 import 'package:sembast/sembast.dart';
 import 'package:sembast_sqflite/sembast_sqflite.dart';
 import 'package:sqflite/sqflite.dart' as sqflite;
-import 'package:sqflite_common_ffi/sqflite_ffi.dart';
+import 'package:sqflite_common_ffi/sqflite_ffi.dart' hide Database;
 
 class OfflineDatabase {
   static final OfflineDatabase instance = OfflineDatabase._internal();