Fifteen years ago today, on October 23rd, 2001, Steve Jobs stood up on stage and announced the original iPod. Since that day, the iPod has changed the way people buy and listen to music, sold millions of devices, and laid the foundation for the powerhouses that Apple has had with the iPhone and iPad.

And while the classic iPod design was finally retired two years ago, and the remaining members of the iPod line are less important to Apple's strategy today than they were years ago, it's still an integral part of history, both for the company and the larger tech industry.

So here's a look back at some highlights in the history of the king of MP3 players, from the physically scrolling plastic wheel of the original iPod to the smooth glass and aluminum of today's iPod Touch.

iPod (first generation) [2001]

The one that started it all, the original iPod launched exactly 15 years ago today for $399. It featured a 5GB hard drive, a FireWire port for syncing, and a physically rotating scroll wheel. A slightly updated second-generation version swapped the scroll wheel for a touch-based one and added Windows support.

iPod (third generation) [2003]

The first major redesign for the iPod, and perhaps the farthest departure from the now iconic clickwheel that's associated with the product, the third generation moved the media controls as separate touch-sensitive buttons on top of the scroll wheel. It also introduced the now-defunct 30-pin iPod connector, which would be the port of choice for all of Apple's mobile devices until the Lightning connector was introduced in 2012.

iPod Mini [2004]

The iPod mini was a smaller, thinner iPod with less storage (either 4GB or 6GB), but came in a variety of fun colors. More importantly, it's the first iPod model to introduce the click wheel, which would remain a staple of the iPod design for the rest of the product's history.

iPod (fourth generation) [2004]

The fourth generation iPod is probably the image most people have in mind when they think of an iPod: a white plastic front with a gray click wheel. Available first in a black and white version, followed by a later iPod Photo model with a color screen.

iPod (U2 Edition) [2004]

Apple also famously released variant U2 editions of the fourth-generation iPod (both B/W and color models) and the later fifth-generation iPod in a special black and red color scheme, along with laser-etched signatures of the band on the back of the case.

iPod Shuffle (first generation) [2005]

The original iPod Shuffle was the first iPod to use flash memory, and also literally looked like a flash drive, complete with removable USB cap. With no screen, it was introduced as a lower cost, budget model iPod, a role its successor still fulfills in the product lineup today.

iPod Nano (first generation) [2005]

The iPod Mini was small, but a the iPod Nano looked almost impossibly thin when it was first released. (It was 0.3 inches thick.) The original Nano was only available in black or white, but a second-generation model brought back the colorful aluminum casing that the Mini had popularized.

iPod (fifth generation) [2005]

The fifth-generation iPod got a wider body and screen as Apple turned its attention to video, adding TV shows, music videos, and later on, full movies to the iTunes Store. The fifth-generation model also was the first full-size iPod model to also come in black, in addition to the original white.

iPod Touch (first generation) [2007]

Released a few months after the original iPhone, the iPod Touch offered a similar iOS experience for users that didn't want to get on board just yet with Apple's vision of the cellular future.

iPod Classic [2007]

The last model of the original iPod, the iPod Classic refreshed the software and replaced the plastic front casing with aluminum. The highest capacity model offered 160GB of storage, which remains the highest capacity iPod ever sold. It was discontinued in September 2014.

iPod Nano (fifth generation) [2009]

Apple used the Nano brand to experiment a lot with various form factors, including the squashed third-gen Nano, and the elongated fourth-generation model. A fifth-generation refresh added a video camera and a speaker.

iPod Touch (fourth Generation) [2010]

The second and third-generation iPod Touch models offered a new tapering design and speaker, with increasingly more powerful hardware that would trickle down from improvements to the iPhone. The fourth-generation Touch would further slim down the design, along with adding both front- and rear-facing cameras for FaceTime support and a Retina display.

iPod Shuffle (fourth generation) [2010]

After the odd third-generation Shuffle, which removed the physical buttons from the device entirely to rely on headphone controls, Apple's current iPod Shuffle is similar to the second-generation design, a small, clip-on device with hardware controls.

iPod Nano (seventh Generation) [2012]

The current Nano resembles an iPod Touch in form factor with a touchscreen and home button, but lacks most of the software functionality of the more powerful iOS devices.

iPod Touch (sixth generation) [2015]

The fifth-generation iPod touch changed out the classic iPod-esque glossy aluminum back for more colorful brushed aluminum. The current sixth-generation model introduced last year uses a similar design but upgraded the processor to the iPhone 6's A8 chip. (The current iPhone 7 uses an A10 Fusion processor, two generations ahead.)