After 15 years as CEO of Apple, Tim Cook has officially handed over the reins to his successor, John Ternus. 

During his stint at the tech giant, Cook helped cement Apple as one of the biggest and most profitable companies in the world. 

So, what was the secret to his success? His morning routine. 

In a Community Letter shared by Apple, Cook revealed exactly how his mornings looked while leading the company. 

'For the past 15 years I've started just about every morning the same way,' he explained.

'I open my email and I read notes I received the day before from Apple's users all over the world.'

However, if you're not an early bird, the billionaire's routine might not be one for you.

Previously speaking to Jessie and Lennie Ware on the Table Manners podcast, Cook explained that he always starts his day at 5am.

Speaking on the podcast last year, Cook called his mornings the 'part of the day that I can control the most.'

'As the day starts to unfold, it becomes less predictable,' he explained.

'And by the end of the day, all these things can commandeer your time and intention and energy. 

'And so I love the part of the day that I can kind of block out the world and focus on a few critical things and just be silent for a while.'

'You thank me for the ways Mac has changed what you can do at work and sometimes give me a hard time because something you care about isn’t working like it should.

'In every one of those emails I feel the beating heart of our shared humanity.

'I feel a sense of deepening obligation to work harder and push further. 

'But most of all, I feel a gratitude that I cannot put into words, that I somehow got to be the person on the other end of those emails, the leader of a company that ignites imaginations and enriches lives in such profound ways it defies description. 

'What an honor and a privilege it has been.'

In terms of his cereal of choice, he explained on Table Manners: 'Kashi, it's a protein–based cereal and unsweetened almond milk. It's very good for me.'

Cook has officially handed the reins to Apple's new CEO, John Ternus, who has spent more than two decades at Apple, previously serving as its senior vice president of hardware engineering.

Ternus joined Apple in 2001 and has risen through the ranks to become one of the company's most important hardware executives, playing a role in the development of products including the iPhone, iPad and Mac.

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