Elon Musk is working to revolutionize transportation both on Earth, through electric car maker Tesla -- and in space, via rocket producer SpaceX. He owns about 25% of Tesla between stock and options, but has pledged more than half his stock as collateral for loans; Forbes has applied a discount to take the loans into account. Twitter's board agreed to sell the company to Musk for $44 billion on April 25, 2022, after he disclosed a 9.1% stake and threatened a hostile takeover. SpaceX, Musk's rocket company, is valued at $100 billion after a funding round in December 2021. He grew up in South Africa, then immigrated to Canada at age 17. He landed in the U.S. as a transfer student to the University of Pennsylvania.
