diff --git a/README.md b/README.md
index 4089f6e..1dacd66 100644
--- a/README.md
+++ b/README.md
@@ -107,13 +107,15 @@ function AwaitedComponent() {
 - Simple APIs and you just read all of them
 - No dependency but React 16.8 or higher and [tslib](https://github.com/Microsoft/tslib) for TypeScript projects
 - Strongly typed with TypeScript. As long as store types are specified, other types can be inferred so you don't have to `as` or `any` anymore!
+- Nested providers. Inner provided stores will override outer stores.
 - (WIP) Basic SSR utilities support
 
 # Common Pitfalls
 
-- To avoid unnecessary re-renders, `StoreProvider` is designed to only re-render when the current and previous `stores` are different. For two `Store<any>[]` *a* and *b*, `a differs from b` is equivalent to `a.length === b.length && for i from 0 to a.length-1, a[i] === b[i]`.
+- Under the hood, the provided stores will be stored in a `Map` with store's constructor as the key and store instance itself as the value. To avoid unnecessary re-renders, `StoreProvider` is designed to cache inner context and only reassign context only if the provided maps are different. Two maps are different if they have different length, or contains different stores. 
 - Once the promise returned by `setState` resolves, it is guaranteed for components that use render props and HOC that have updated, but these using `useStore` hook will not have the guarantee. I am working on it.
 
+
 ## Roadmap
 
 - [x] Store and `useStore` hook
diff --git a/package.json b/package.json
index 9a3f384..94d73c2 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,7 @@
     "clean:dist": "rimraf dist",
     "watch": "rollup -cw",
     "start": "rollup -cw",
-    "lint": "tslint 'src/**/*.{ts,tsx}' --fix",
+    "lint": "tslint '{src,tests}/**/*.{ts,tsx}' --fix",
     "test": "jest",
     "coveralls": "jest --coverage && cat ./coverage/lcov.info | coveralls",
     "release": "yarn run build && standard-version"
@@ -30,13 +30,13 @@
     "tslib": "^1.9.3"
   },
   "peerDependencies": {
-    "react": ">=16.8.0"
+    "react": ">=16.8.1"
   },
   "devDependencies": {
-    "react": ">=16.8.0",
+    "react": ">=16.8.1",
     "@types/enzyme": "^3.1.17",
-    "@types/jest": "^24.0.0",
-    "@types/react": ">=16.8.0",
+    "@types/jest": "^24.0.1",
+    "@types/react": ">=16.8.2",
     "@types/react-test-renderer": "^16.8.0",
     "coveralls": "^3.0.2",
     "cross-env": "^5.2.0",
diff --git a/src/StoreProvider.tsx b/src/StoreProvider.tsx
index 10d48a7..36a4861 100644
--- a/src/StoreProvider.tsx
+++ b/src/StoreProvider.tsx
@@ -10,48 +10,62 @@ interface Props {
   children: React.ReactNode;
 }
 
-// interface State {
-//   map: ISimstateContext;
-// }
+interface State {
+  map: ISimstateContext;
+}
 
-function arrayEquals<T>(array1: T[], array2: T[]) {
-  const len = array1.length;
-  if (len !== array2.length) {
+function contextEqual(a: ISimstateContext, b: ISimstateContext) {
+  if (a.size !== b.size) {
     return false;
   }
-
-  for (let i = 0; i < len; i++) {
-    if (array1[i] !== array2[i]) {
+  for (const [key, val] of a) {
+    if (b.get(key) !== val) {
       return false;
     }
   }
 
   return true;
-
 }
 
-function constructMap(stores: Store<any>[]) {
-  const map: ISimstateContext = new Map();
-  stores.forEach((store) => {
-    map.set(store.constructor as StoreType<any>, store);
-  });
-  return map;
+interface InnerProps {
+  currentMap: ISimstateContext;
 }
 
-export default class StoreProvider extends React.Component<Props> {
+class StoreProvider extends React.Component<InnerProps, State> {
 
-  shouldComponentUpdate(prevProps: Props) {
-    return !arrayEquals(prevProps.stores, this.props.stores);
+  componentDidUpdate() {
+    if (!contextEqual(this.props.currentMap, this.state.map)) {
+      this.setState({ map: this.props.currentMap });
+    }
   }
 
-  render() {
-
-    const map = constructMap(this.props.stores);
+  state = { map: this.props.currentMap };
 
+  render() {
     return (
-      <SimstateContext.Provider value={map}>
+      <SimstateContext.Provider value={this.state.map}>
         {this.props.children}
       </SimstateContext.Provider>
     );
   }
 }
+
+function constructMap(prev: ISimstateContext | undefined, stores: Store<any>[]): ISimstateContext {
+  const map: ISimstateContext = new Map(prev!); // new Map(undefined) will work
+
+  for (const store of stores) {
+    map.set(store.constructor as StoreType<any>, store);
+  }
+
+  return map;
+}
+
+export default (props: Props) => (
+  <SimstateContext.Consumer>
+    {(map) => (
+      <StoreProvider currentMap={constructMap(map, props.stores)}>
+        {props.children}
+      </StoreProvider>
+    )}
+  </SimstateContext.Consumer>
+);
diff --git a/tests/provider.spec.tsx b/tests/provider.spec.tsx
index 790cea8..5f1962f 100644
--- a/tests/provider.spec.tsx
+++ b/tests/provider.spec.tsx
@@ -43,25 +43,27 @@ describe("Provider", () => {
 
     expect(wrapper.find("span").text()).toEqual("43");
 
-    wrapper.setProps({ stores: [new TestStore(43), new AnotherStore() ] });
+    wrapper.setProps({ stores: [new TestStore(43), new AnotherStore()] });
 
     expect(wrapper.find("span").text()).toEqual("43");
   });
 
   it("should not re-render if the input store hasn't changed", () => {
 
-    function Child() {
-      return (
-        <SimstateContext.Consumer>
-          {(map) => {
-            return (
-              <span>{map!.get(TestStore)!.state.value}</span>
-            );
-          }
-          }
-        </SimstateContext.Consumer>
-      );
+    class Child extends React.PureComponent {
+      render() {
+        return (
+          <SimstateContext.Consumer>
+            {(map) => {
+              return (
+                <span>{map!.get(TestStore)!.state.value}</span>
+              );
+            }}
+          </SimstateContext.Consumer>
+        );
+      }
     }
+
     class Component extends React.Component<{ store: Store<any> }> {
       render() {
         return (
@@ -85,4 +87,60 @@ describe("Provider", () => {
 
   });
 
+  it("should support nested providers", () => {
+    class AnotherStore extends Store<{ text: string }> {
+      constructor(text: string) {
+        super();
+        this.state = { text };
+      }
+    }
+
+    function Child() {
+      return (
+        <SimstateContext.Consumer>
+          {(map) => (
+            <div>
+              <span id="TestStore">{map!.has(TestStore) ? map!.get(TestStore)!.state.value : "no"}</span>
+              <span id="AnotherStore">{map!.has(AnotherStore) ? map!.get(AnotherStore)!.state.text : "no"}</span>
+            </div>
+          )}
+        </SimstateContext.Consumer>
+      );
+    }
+
+    const test = (Parent: React.ComponentType, testStore: string, anotherStore: string) => {
+      const wrapper = mount(<Parent />);
+
+      expect(wrapper.find("#TestStore").text()).toEqual(testStore);
+      expect(wrapper.find("#AnotherStore").text()).toEqual(anotherStore);
+    };
+
+    const Parent1 = () => (
+      <StoreProvider stores={[new TestStore(42)]}>
+        <Child />
+      </StoreProvider>
+    );
+
+    test(Parent1, "42", "no");
+
+    const Parent2 = () => (
+      <StoreProvider stores={[new AnotherStore("hahaha")]}>
+        <Parent1 />
+      </StoreProvider>
+    );
+
+    test(Parent2, "42", "hahaha");
+
+    const Parent3 = () => (
+      <StoreProvider stores={[new AnotherStore("outter")]}>
+        <StoreProvider stores={[new AnotherStore("inner")]}>
+          <Child />
+        </StoreProvider>
+      </StoreProvider>
+    );
+
+    test(Parent3, "no", "inner");
+
+  });
+
 });
diff --git a/tsconfig.json b/tsconfig.json
index 0245932..50d5080 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -10,9 +10,10 @@
     "noUnusedLocals": true,
     "strictNullChecks": true,
     "esModuleInterop": true,
+    "downlevelIteration": true,
     "sourceMap": true,
     "declaration": true,
-    "importHelpers": true
+    "importHelpers": true,
   },
   "include": [
     "src/**/*.tsx"
diff --git a/tslint.json b/tslint.json
index 22aa7de..1e532e6 100644
--- a/tslint.json
+++ b/tslint.json
@@ -14,7 +14,7 @@
     "member-ordering": false,
     "no-empty": false,
     "no-console": false,
-    "max-classes-per-file": [ true, 3],
+    "max-classes-per-file": false,
     "jsx-no-multiline-js": false,
     "jsx-alignment": false,
     "jsx-no-lambda": false,