When you start exploring React Native its Navigation can be somehow confusing.
Let's just say it has its issues, but rest assured that the React Native team is on track.

Still, it's such a core problem/feature that it gained much attention from the community, with some great components and luckly some tutorials.
The most complete and comprehensive example we're showing here, coded and written by Brian Leonard from TaskRabbit.

React Native Example App: Navigation blog post

ReactNativeSampleApp on GitHub

At TaskRabbit, we are trying to understand the best way to build React Native apps. This app is a working app in which we implement new ideas or those that have worked for us so far. We'll write about it on our tech blog.

The app itself is vaguely like twitter/tumblr. There are users that make posts. They follow other users. You can look at follows and their posts. The features (or styling) isn't the main point. At this time, we're mostly demonstrating architectural concepts.