After uncommenting the code for [part 3](https://github.com/leanjscom/fb-messenger/tree/styling-in-react#part-3-refactoring), running `npm start` throws errors:  When you `npm install` you can see this peer dependency error: > npm WARN styled-components@4.1.2 requires a peer of react-dom@>= 16.3.0 but none is installed. You must install peer dependencies yourself Updating this in package.json works :+1: