John Ternus is now the CEO of Apple

Apple SVP John Ternus takes over as CEO from Tim Cook. | AFP via Getty Images For the first time since 2011, one of the world's most valuable companies has a new leader, as today marks John Ternus' first day as Apple's CEO. He's replacing Tim Cook, who will continue on as the executive chairman on Apple's board and departed with a letter to employees that remarked, "This place is proof that culture triumphs over everything.