Mac OS X 10.5 Leopard was released on October 26, 2007 after a lengthy development cycle that Apple said was slowed by the release of the original iPhone. When it did ship, Leopard was a major push forward for OS X.
Gone were the numerous window styles that had cropped up in the Panther and Tiger years. Every major application and window were now using a new gray appearance that gave the whole OS a more mature look. Beyond window styles, Leopard brought a new Dock, which included Stacks, a way to look into a folder stored in the Dock.
The release also brought automated backups with Time Machine, a redesigned Finder complete with Cover Flow and Quick Look, Photo Booth, an expanded Mail that now supported things like notes and RSS feeds and Spaces, Apple’s take on virtual desktops.