Cook has actually taken over the CEO reins from Jobs before: for 2 months in 2004, while Jobs was recovering from surgery for pancreatic cancer.

Cook turned 48 in November and the Fortune article described him as a "fitness nut" and "intensely private."

He's from Alabama and is a 1984 engineering graduate of Auburn University.

Cook was hired by Apple a decade ago to deal with the mess of Apple's manufacturing and distribution operations and its supply chain. The coolest products in the world are useless unless they meet quality criteria, can be manufactured efficiently with strict cost controls, and an entire set of complex inter-relationships deliver the product efficiently, on time, to everyone who wants one. Fortune tracked some data that showed Cook has been very successful in keeping inventory low and profit margins high, both highly desirable trends.

The article mentions one meeting of his team to talk over a problem in China. According to Fortune, Cook told the group, "This is really bad. Someone should be in China driving this." Thirty minutes later, he glanced at Sabih Khan, a key operations executive, "and abruptly asked, without a trace of emotion, 'Why are you still here?'