Google’s Android operating system has undergone a pretty incredible metamorphosis since it debuted on the T-Mobile G1, which celebrates its fifth anniversary this week. Half a decade might seem like a long time, but on the scale of the PC's growth, it's a blink of an eye. You could make a pretty convincing argument that no consumer technology in history has evolved as quickly as the smartphone, and Android has been at the very center of that evolution.

With the release of Android 4.4 — KitKat — on Google's new Nexus 5 smartphone, we wanted to take a look back through the years at how Andy Rubin’s brainchild has evolved into the industry titan that it is today. What’s changed? What has (sometimes stubbornly) stayed the same?