Tim Cook Steps Down as Apple CEO, Handing Reins to John Ternus

Tim Cook has officially stepped down as CEO of Apple after a 15-year tenure. John Ternus, a long-time hardware executive, will take over starting today. During his time at the helm, Apple's stock gained nearly 2,300%, with the popularity of iPhones driving growth.

Cook will shift to executive chair of Apple's board and remain involved in talks with world governments. He took over after Steve Jobs resigned on August 24, 2011.

Ternus is set to face his first test at Apple's annual product event next week, where the company is expected to announce an update to its iPhone lineup, potentially including a foldable iPhone.