The iPod, which celebrated its 10th birthday on Sunday, may not have been the first portable music player, or even the first to play digital music files. But it's the one that everyone remembers, and will go down in history as one of the most significant technology launches of the 21st century.

Sure, there was the Sony Walkman. It played cassette tapes, and everyone had one, but no one fondly remembers the Walkman's industrial design. Nor was the Walkman even the first mobile music device. That distinction goes to various portable vinyl players -- yes, vinyl! -- that floated around during the pre-Walkman era.

The iPod, though, was the most revolutionary portable music player of all, and vividly demonstrated Apple's authority as a consumer electronics manufacturer. When it launched, the iPod was able to benefit from the rogue music distribution of peer-to-peer file-sharing services like Napster, and that helped provide a foothold.

But the iPod's real success enabler was iTunes, a fully curated platform with buy-in from the music industry. And then there was the device's industrial design. The first iPod was an object of techno-lust, and the product line's design has only become more enchanting.

Available in some two dozen iterations over the years, the iPod made music accessible to everyone. In short order, there was an option for every budget, and for every application: an iPod Classic with up to 160GB of storage (that’s 40,000 songs) for true music aficionados and DJs; smaller, sporty shuffles and nanos, perfect for exercising and extreme mobility; and eventually the iPod touch for playing games and watching videos.

It's a breathtaking product catalog. So let's take a look at how the iPod has evolved over the years, and where it's headed next.