Stephen Hackett:

Building a new operating system is a monumental challenge, and in January 2000 when Aqua was introduced, Apple was in the thick of the transition to OS X.

Beyond the staggering amount of development work taking place to smash Mac OS and NeXTSTEP together, Apple was hard at work on the user interface of OS X. But to understand what OS X would become (and how it would look), it’s important to remember where the company had been before.

Well-researched retrospective of Apple’s work on the Aqua interface over the years. I enjoyed the collection of screenshots and links, and it’ll be interesting to see where Apple will take Aqua with the next OS X.