Eliot Van Buskirk tells The Secret of the iPod's Scroll Wheel.

The iPod's scroll wheel has been through three iterations. The first one actually rotated; then there was the touch-sensitive one; and finally there's the clickable one found on the iPod Mini and fourth-generation iPod. I'd always assumed that this bit of design genius sprang from Apple Computer's labs. But in fact, I discovered that a company called Synaptics, which primarily makes touchpads for laptops, actually perfected this little piece of navigational heaven, in accordance with Apple's stringent design requirements.