* Ability to return multiple elements from `render()`.
* Better support for error boundaries.
You can read more about it in [React Fiber Architecture](https://github.com/acdlite/react-fiber-architecture). While it has shipped with React 16, the async features are not enabled by defaut yet.
You can read more about it in [React Fiber Architecture](https://github.com/acdlite/react-fiber-architecture). While it has shipped with React 16, the async features are not enabled by default yet.
Its source code is located in [`packages/react-reconciler`](https://github.com/facebook/react/tree/master/packages/react-reconciler).