This is one of the best tutorials I’ve found so far for describing how to make an isomorphic React app (AKA, SSR, Server-Side Rendering). It goes step-by-step, explaining what you’re trying to accomplish, and builds up from a basic “Hello, World” example, then adding initial data state, adding a component that fetches dynamic data, URL routing, and maintaining state between server and browser rendered views. Along the way, it covers various pitfalls and how/why to work around them.

Server Rendering with React and React Router