Based in the San Francisco Bay Area, Calico rapidly expanded and had more than 150 employees by 2018. The biotech firm renewed its collaboration with AbbVie for another three years, with the companies making a joint $1 billion (£797m) pledge to target so-called ‘cellular stresses’ and develop anti-ageing drugs.

But it hasn't all been plain sailing for Calico. After a string of its top executives left for other positions, some people began to criticise the company's approach – and in 2020, Maris himself (pictured) admitted he was "disappointed" with Calico's lack of results. Maris previously hit headlines when it was revealed that he'd chosen not to invest in Theranos, the biotech start-up launched by disgraced Silicon Valley billionaire Elizabeth Holmes.

From Elon Musk to Jeff Bezos: the super-rich using tech to live forever