Apple's Tim Cook told employees that he will miss the role of chief executive officer but has "enormous comfort" in the leadership of his replacement, John Ternus, according to Bloomberg. Cook made the comments in an email to all employees on Monday, his final day as CEO. He took over from Steve Jobs in August 2011, embarking on a record-breaking 15-year tenure that included the launch of the Apple Watch and AirPods and major expansions to the iPhone, iPad and Mac lines.

"As you know, I am not leaving Apple. But I am stepping away from a role that I have loved deeply," Cook said in the email, adding that he will miss the work in ways he can only begin to imagine even as he remains completely at peace with his decision. Discussing Ternus, Cook said few people understand what it takes to build products that change the world the way John does, and that he could not be more excited for his leadership.

In his new role as executive chairman, Cook will remain responsible for working with governments around the world, including those of the US and China. In the memo, he thanked employees for the privilege of a lifetime serving as their leader, said the company is proof that culture triumphs over everything, and expressed hope that they will continue to be proud to be part of Apple and always give it their best.