Version 10.0/10.1: "Cheetah/Puma"
March 24, 2001 saw the release of Mac OS X 10.0, internally known as Cheetah. Initially, it was a mess, and lots of critics panned it. Mac enthusiasts disagreed, seeing it as a breath of fresh air and having wanted a Mac OS overhaul for years. Version 10.1, Puma, released September 25, 2001, would keep the same artwork, but was vastly improved.

Version 10.2: "Jaguar"
On August 24, 2002, it was with Mac OS X v10.2, or Jaguar, that Apple would use the code name as part of the actual branding. This edition saw features added that we have come to know frequently over the years, such as Address Book and iChat.

Version 10.3: "Panther"
In what was starting to become a yearly tradition, we again saw another update of OS X on October 24, 2003, with Panther. There were many performance updates, and new features such as FileVault, Safari, iChat AV, as well as more Windows interoperability.

Version 10.4: "Tiger"
On April 29, 2005, just shy of being two years later, Tiger would bring about an Apple stated more than 150+ new features. We would be introduced to the likes of Spotlight, QuickTime 7, Safari 2, Automator and a host of others.

Version 10.5: "Leopard"
Leopard would need a couple of years to be released into the wild on October 26, 2007. Deemed by Apple as "the largest update of Mac OS X," it was said to have brought more than 300 new features to the table. Some of those features included an updated Finder, Time Machine, Spaces and Boot Camp.

Version 10.6: "Snow Leopard"
The first to feature the feline as part of the box artwork, Snow Leopard was released on August 28, 2009. This version wasn't as much about appearance changes, but rather changes "under the hood". Snow Leopard's main M.O. was to increase performance, efficiency and stability.

Version 10.7: "Lion"
We learned today that Lion will only be available for download from the Mac App Store, which means there's no box artwork to display. No worries, however, as more than 250 new features will make their way into the latest version, set to be released into the wild next month!