Tim Cook's last day as Apple CEO: How he led the tech giant's rise to $4T

Apple CEO Tim Cook is stepping down from his role at the helm of one of the world's largest tech companies after a 15-year tenure that saw Apple become the first publicly traded U.S. company with a $1 trillion market cap and other notable milestones.

He announced in April that he would step down as Apple CEO at the end of August, and while he is leaving that role, he will remain with the company as the executive chairman. John Ternus, who most recently served as Apple's senior vice president of hardware engineering, will be Cook's successor.