Elon Musk experienced significant bullying in high school due to his intellectual pursuits and unique personality. He was often the smallest and youngest in his class, and his focused nature, which led him to be engrossed in his own thoughts, made him an easy target. He was also reportedly disliked by popular jocks, and some of the bullying resulted in him being hospitalized for injuries.

Elon Musk lived on $1 a day when he moved to Canada as a teen and more surprising facts about his youth

Over the past two decades, as he became the richest person in the world, Elon Musk launched or led companies such as PayPal, SpaceX, Tesla, and Twitter. His success as a serial entrepreneur follows an eventful childhood in which a young Musk played with homemade rockets, coded his own video games and endured hardships both at school and home.

Here are several facts you might not know about Musk’s youth.

1. He went door-to-door selling candy to rich people

While growing up in Pretoria, Musk, his brother Kimbal and their cousins traveled around the wealthy parts of the South African capital selling homemade chocolate Easter eggs.

The adventurous group traveled door-to-door, selling the sweets for 20 times the cost of making them.

“I’d make them for 50 cents and charge $10 for an Easter egg and I’d always get this question like, ‘Why are you charging $10 for this little Easter egg?’” said Kimbal to CNBC Make It in a 2017 interview. “And I was like, ‘Well, you’re supporting a young capitalist. And the reality is if you don’t buy it from me, you’re not going to get one — and I know you can afford $10.’”

2. He was bullied

As he discussed in an interview on “60 Minutes,” Musk had, in some ways, a challenging childhood. While he attended grade school in Pretoria, South Africa, Musk was not only the youngest and smallest kid in his class, but he was nerdier and much more into books than many jocks at school.

In Ashlee Vance’s 2015 book “Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future,” Musk said gangs of boys at would sometimes hunt him down, going so far as to push him down a flight of stairs in one instance and send him to the hospital. “I was almost beaten to death,” he added on “60 Minutes.”

The bullying continued until he was 15 years old, when went through a growth spurt and learned how to defend himself by doing karate, judo and wrestling. By 16, he said he was “dishing it out as hard as they’d give it to me.”

3. His parents thought he was deaf

Musk was so introspective as a kid that his parents and doctors ordered tests to check if he was deaf. His mother Maye Musk eventually learned this was his way of daydreaming about his inventions.

“He goes into his brain and then you just see he is in another world. He still does that. Now I just leave him be because I know he is designing a new rocket or something,” recalled Maye Musk in Vance’s book.

Though this bothered his peers, who could reportedly yell at him and do jumping jacks beside him and he wouldn’t notice, Musk’s pensive moments allowed him to visualize projects he’d hope to tackle.

4. He made his own explosives and rockets

While his parents were away, Musk lived mostly under the watch of a housekeeper. According to Musk, she was mainly there to make sure he didn’t break anything.

“She wasn’t, like, watching me. I was off making explosives and reading books and building rockets and doing things that could have gotten me killed,” said Musk. “I’m shocked that I have all my fingers.”