How much is Elon Musk worth, and where did his fortune come from?

Elon Musk has quickly become one of the world's most well-known entrepreneurs and industrialists. In little more than a decade Musk made a success of the Tesla electric car company, and is now at the forefront of rocket launching (and landing) with his other company, SpaceX.

The 45-year-old is also working on a new type of solar roof panels which look just like regular tiles, came up with the 700mph 'hyperloop' train, is exploring ways to increase tunnel boring speeds to house underground roads, and plans to make humans a multi-planetary species by colonising Mars.

How much is Elon Musk worth and where did his fortune come from?

At the time of publication, Musk is worth $13.5bn (£10.9bn), according to the regularly-updated Forbes list of the world's billionaires. Musk is the 87th richest person in the world, slightly above Rupert Murdoch but some way behind the better-known billionaires of Silicon Valley, such as Google founders Sergey Brin and Larry Page ($40bn each), and Facebook boss Mark Zuckerberg ($58.6bn).

PayPal

Musk began earning money at the age of 12 when he sold the code for a video game he had created called Blastar, to a computer magazine for $500. Musk then set up a web software company called Zip2 with his brother Kimbal in 1995, aged 24. Compaq acquired Zip2 in 1999, just months before the dot-com bubble burst, for over $300m. Musk received $22m from the sale.

A month later, in March 199, Musk co-founded X.com, an online financial services company which made payments possible via email. In 2000 the company merged with another firm called Confinity, which was developing a money transfer service called PayPal. Two years later, PayPal was purchased by eBay for $1.5bn in stock, of which Musk received $165m.

SpaceX

In 2001 Musk began thinking about space travel and taking humans to Mars; a year later he founded Space Exploration Technologies, now known as SpaceX. In 2008 SpaceX puts its first satellite into orbit and in 2012 it became the first commercial company to launch a rocket bound for the International Space Station.

In 2016 Musk outlines his plans for first sending cargo and then humans to Mars. He wants to establish a colony of 80,000 people by 2014 and plans to begin unmanned missions in 2018, before transporting humans to the Red Planet in 2024. Musk has said several times that he would like to die on Mars, just "not on impact".

Tesla

Meanwhile, electric car startup Tesla Motors was founded in 2003 by Martin Eberhard and Marc Tarpenning. Musk led a Series A funding round in early 2004, joining the Tesla board of directors as chairman. He became chief executive after the 2008 financial crisis and still holds that position at the time of publication. Since 2008 Musk has overseen the launch of the Model S saloon car and Model X sports utility vehicle, and will soon begin selling the Model 3, the cheapest Tesla yet.

Musk earns a salary from Tesla of just $1 per year, but also receives stock options and performance-based bonuses, as Steve Jobs did when he ran Apple. By late 2016 Musk had amassed Tesla shares equal to about 22% of the entire company, worth around $9.5bn.

The Boring Company

In late 2016 Musk tweeted about how bad the traffic was in Los Angeles and suggested he could build tunnels for underground roads. A few weeks later, Musk had hired boring equipment and dug a large hole in the SpaceX car park. He believes he can improve tunnel boring speed by a factor of 10 but is yet to say how he plans to commercialise such technology.