The UI system in WatchKit is entirely linear. When you add interface objects, they stack from top to bottom. You can adjust the relative positioning, but sometimes you’ll want more control over things. That’s where groups come in. The WKInterfaceGroup object acts as a container for other objects, letting you adjust the positioning and size of elements in more precise ways. You can set background colors and images for groups, hide them from your UI, and even nest groups together. In this chapter, you’ll see the capabilities of groups, making interesting user interfaces possible.