The Wired blog has put together a gallery of 17 photos documenting the evolution of the computer mouse over the past 45 years. It all started with a simple wooden device created by Douglas Engelbart and Bill English in a Stanford laboratory. Back then, of course, the first "mouse" was actually known as the "bug." Here it is, shown in cross-section in all its wooden glory, being held by Douglas Engelbart. Inside, you can see the patented mechanism that tracks its movement.
Over the next several decades, the device "evolved" into various shapes and configurations, including new buttons that could be used for tasks such as gaming as well as for navigation. During some periods, ergonomic design and aesthetic value became central concerns, while in other iterations, the focus was on pure functionality.