Apple's (AAPL) Tim Cook is stepping down from his role as CEO, handing over the reins of the $4 trillion company to senior vice president of hardware engineering John Ternus.

Rumors have been swirling since at least 2024 that Ternus was up for the chief executive position, and that will officially become reality on Sept. 1.

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While he holds one of the larger leadership roles at Apple and makes appearances at the company's high-profile product launches, including last March's debut of the MacBook Neo, Ternus is still a relative unknown for those who haven't been closely following the company in recent years.

The incoming CEO joined Apple in 2001 as a member of the company's product design team before being elevated to vice president of hardware engineering in 2013. He was named senior vice president of hardware engineering in 2021.

Ternus graduated from the University of Pennsylvania with a degree in mechanical engineering and worked at Virtual Research Systems before moving to Apple.

He's also the kind of perfectionist Apple embraces.

John Ternus, Apple's senior vice president of hardware engineering, introduces the M2 microprocessor at Apple's WWDC 2022 developer conference at the company's headquarters in Cupertino, Calif. (Christoph Dernbach/picture alliance via Getty Images) · picture alliance via Getty Images

During his keynote address at the University of Pennsylvania's engineering commencement in 2024, Ternus recounted arguing with a supplier over the number of grooves in the heads of screws that would sit in the back of his first Apple product, the Apple Cinema Display. The screws the supplier offered had 35 grooves, but Ternus demanded they stick to the 25 grooves Apple wanted.

"I distinctly remember stepping back for a minute and thinking to myself, 'What the hell am I doing? Is this normal?' And I thought about it, and I realized it might not be normal, but it's right," he said.

"It's right because I'd already spent months working on that product, and if you're going to spend that much time on something, you should put in your very best effort," he said. "Maybe a customer notices, maybe they don't. But either way, whenever I saw one of those displays on someone's desk, it mattered to me to know that my teammates and I had considered everything about it."

Apple has credited Ternus with a variety of recent successes, including helping to make the Mac lineup the most popular it's ever been, introducing the iPhone 17 lineup, and improving the AirPods.

The company said Ternus also helped push Apple to develop a recycled aluminum compound that it uses across a number of products. He also worked on the 3D-printed titanium in the Apple Watch Ultra 3.

Ternus will be leading the company during a time of major upheaval in the tech industry, driven by artificial intelligence.