Elon Musk. Reuters

Elon Musk is the founder of one of the most valuable tech companies in the world.

But his rise to success wasn't so easy.

A new book written by Bloomberg technology reporter Ashlee Vance, “Elon Musk: Tesla, SpaceX and the Quest for a Fantastic Future,” is filled with anecdotes about SpaceX, PayPal, Tesla Motors, and more.

She also talks about Musk's childhood, which the New York Times describes as "excruciating," and shows just how resilient Musk is.

Born in Pretoria, South Africa, Musk was a "bookish" and awkward young boy, interested in computers and sci-fi. His father was emotionally abusive and tough on his children, allegedly ordering Musk and his brother "to sit silent for four hours as he lectured them," according to the Washington Post.

Musk was also viciously bullied in school. His classmates pushed him down a concrete stairwell. In one instance, he was beaten so badly that he needed to go to the hospital.

Here's Musk recounting that horrific experience:

“They got my best [expletive] friend to lure me out of hiding so they could beat me up. And that [expletive] hurt. For some reason they decided that I was it, and they were going to go after me nonstop. That’s what made growing up difficult. For a number of years there was no respite. You get chased around by gangs at school who tried to beat the [expletive] out of me, and then I’d come home, and it would just be awful there as well.”

His difficult experiences both at home and school would eventually lead Musk to leave South Africa for the United States.