Elon Musk, a South African-born engineer, inventor and billionaire, is one of the most important entrepreneurs in the world.

But the 47-year-old is no stranger to turmoil,

and by his own account

his career has been full of highs and lows.

“Just three years ago,

I was showering at the Y and sleeping on the office floor.

And now, obviously I've got a million-dollar car

and quite a few creature comforts.”

After making a fortune with his first successful startup, Zip2,

Musk gained fame as the co-founder of PayPal in the late 1990s.

“So this is an ATM. What we're going to do is transform the traditional banking industry.”

The company lost hundreds of millions of dollars,

and Musk was ousted as CEO because of internal turmoil.

But when PayPal went public in 2002,

and then was sold to eBay, Musk — as the biggest shareholder — walked away with $200 million.

By the mid-2000s, Musk had turned around and invested almost all of his PayPal fortune into his new companies:

SpaceX, Tesla and SolarCity.

With SpaceX, Musk's aspiration is out of this world — literally.

It's a commercial space flight company,

which designs and launches advanced rockets into space.

“Behind me is where Falcon 9 would sit during launch.”

One of its ambitions is to eventually send people to Mars.

“And I can't think of anything more exciting than going out there and being among the stars.”

But it has faced some roadblocks.

Their first three rocket launches —

failed, burning through almost all of the company's assets.

But SpaceX has had recent successes.

The Falcon Heavy launch earlier this year was a big milestone and it carried an interesting payload:

a dummy astronaut riding a Tesla car that was orbiting space.

The company has also landed contracts with NASA,

but questions about safety and cost remain.

“We sold over 1,000 cars — and by sold

I mean people put down a substantial deposit on the car.”

Tesla, Musk's electric car company,

is one of the first of its kind to work on a large scale.

It has also successfully disrupted the auto industry.

The company is valued at over $50 billion.

The Tesla Model S has been called

the greatest car ever built.

But Tesla has also faced some setbacks, including

car batteries that caught on fire, recalls and production delays.

SolarCity, Musk's renewable energy venture,

initially had a bright future.

It's the largest provider of rooftop solar systems in the U.S.,

and the company boomed on Wall Street.

But after investors raised doubts about its business model,

SolarCity's shares quickly lost value,

and Tesla had to take over

in what was widely seen as a bailout.

“We really need to make solar panels as appealing as electric cars have become.”

But while Musk may have been flirting with bankruptcy and calamity for years,

his projects continue to captivate the collective imagination.

“Life has to be more than about solving problems.

There have to be things that make you proud to be a member of humanity.”