diff --git a/package.json b/package.json
index b0a111a..9e93908 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@yermak/derived",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "State manager library",
   "main": "./dist/index.js",
   "module": "./dist/index.js",
diff --git a/src/index.ts b/src/index.ts
index c7ec9df..4e40857 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,3 +3,4 @@ export { derived, type DerivedType } from './derived';
 export { async, type AsyncType } from './async';
 export { map, type MapType } from './map';
 export { useObservable, type ObservableType } from './observable';
+export { observer, type Observer } from './observer';
diff --git a/src/map.ts b/src/map.ts
index 5e2f883..1892718 100644
--- a/src/map.ts
+++ b/src/map.ts
@@ -1,4 +1,3 @@
-import { ObservableType } from './observable';
 import { observer } from './observer';
 import { store, StoreType } from './store';
 
@@ -6,11 +5,8 @@ type MapValue<K extends keyof any, V> = Record<K, V>;
 
 type MapItemStore<V> = StoreType<V | undefined>;
 
-export interface MapType<K extends keyof any, V> extends ObservableType<Map<K, StoreType<V | undefined>>> {
+export interface MapType<K extends keyof any, V> {
   item: (key?: K | null | undefined) => MapItemStore<V>;
-  has: (key: K) => boolean;
-  set: (key: K, value: V) => void;
-  delete: (key: K) => void;
 }
 
 export function map<K extends keyof any, V>(initialValue?: MapValue<K, V>): MapType<K, V> {
@@ -18,44 +14,46 @@ export function map<K extends keyof any, V>(initialValue?: MapValue<K, V>): MapT
   type ItemValue = V | undefined;
 
   const _observer = observer<Map<K, ItemStore>>();
+
   const undefinedStore = store<ItemValue>(undefined);
 
   const map = new Map<K, ItemStore>();
-  if (initialValue) {
-    for (let key in initialValue) {
-      const value = store<ItemValue>(initialValue[key]);
-      map.set(key, value);
+
+  const addStore = (key: K, value: ItemValue): ItemStore => {
+    const valueStore = store<ItemValue>(value);
+    map.set(key, valueStore);
+    return valueStore;
+  };
+
+  const getStore = (key: K): ItemStore => {
+    const valueStore = map.get(key);
+    if (valueStore === undefined) {
+      return addStore(key, undefined);
     }
+    return valueStore;
+  };
+
+  for (let key in initialValue) {
+    addStore(key, initialValue[key]);
   }
 
   return {
-    get: () => map,
     item: (key?: K | null | undefined) => {
       if (key === null || key === undefined) {
         return undefinedStore;
       }
-      let valueStore = map.get(key);
-      if (valueStore === undefined) {
-        valueStore = store<ItemValue>(undefined);
-        map.set(key, valueStore);
-      }
-      return valueStore;
-    },
-    has: (key: K) => map.has(key),
-    set: (key: K, value: V) => {
-      const valueStore = map.get(key);
-      if (valueStore === undefined) {
-        map.set(key, store<ItemValue>(value));
-        _observer.notify(map);
-        return;
-      }
-      if (valueStore.get() !== value) {
-        valueStore.set(value);
-        _observer.notify(map);
-        return;
-      }
+      const valueStore = getStore(key);
+      return {
+        set: (newValue) => {
+          if (valueStore.get() === newValue) {
+            return;
+          }
+          valueStore.set(newValue);
+          _observer.notify(new Map(map));
+        },
+        get: valueStore.get,
+        subscribe: valueStore.subscribe,
+      };
     },
-    delete: (key: K) => map.delete(key),
-    subscribe: _observer.subscribe,
   };
 }