Elon Musk, the man behind PayPal, Tesla and SpaceX, is the second richest person in the world. He is an engineer, a charismatic leader and a philanthropist who has a dream that many believe is unreachable: space colonization.

Bill Gates started a business out of a tiny space and grew it into one of the most powerful companies in the world: Microsoft. He went from a quiet computer programmer to the world's richest man and then to a multibillionaire philanthropist.

Mark Zuckerberg was just 19 when he built the social media giant Facebook out of his college dorm. The tech innovator became the planet's youngest billionaire at 23 and changed the world and the internet forever.