"[Tim] Cook is one of the best listeners I've ever encountered," says Kim Scott, author of "Radical Candor" who was a faculty member at Apple University.

Cook exported the smartphone revolution from the US to the world and turned Apple into one of the most powerful and profitable companies on Earth

John Ternus, vice president of hardware engineering, will succeed Cook as CEO on September 1.

Tim Cook's 15-year tenure at the helm of Apple was highly profitable for Wall Street, as the company's market cap swelled from $350 billion to $4 trillion.

CNBC's Jim Cramer reflects on Apple CEO Tim Cook's legacy building the "greatest consumer-based enterprise in history."

"[Tim] Cook is one of the best listeners I've ever encountered," says Kim Scott, author of "Radical Candor" who was a faculty member at Apple University.