For the first two major releases of Android, small screens were it. Then came the Android tablets: devices with screen sizes of 10”. And that complicated things. Why? Because now there was so much screen real estate that a simple activity had a hard time filling a screen while at the same time keeping to a single function. It no longer made sense to have an e-mail application that showed only headers in one activity (filling a large screen), and a separate activity to show an individual e-mail (also filling a large screen). With that much room to work with, an application could show a list of e-mail headers down the left side of the screen and the selected e-mail contents on the right side of the screen. Could it be done in a single activity with a single layout? Well, yes, but you couldn’t reuse that activity or layout for any of the smaller-screen devices.