Over the course of the last three chapters, you have been introduced to the building blocks that you can use to create a simple, single-screen application. This chapter takes the next logical step and looks at how to create multi-screen applications. In UIKit, each screen is built around a view controller, and similarly in WatchKit, each screen is mapped to an interface controller. UIKit offers you several ways to combine view controllers—for example, you can use a UITabBarController to create a tabbed user interface, a to build a hierarchical application, or a UIPageViewController if your application has pages of similar information that you want to be able to swipe through. You are completely free to mix all these different view controllers together or create navigation schemes of your own if you need to.