Elon Musk's unveiling of Tesla's first mass-market vehicle Thursday has been called Musk's "moment of truth," and while it will be a pivotal moment in his career, this is not Musk's first rodeo.

The billionaire entrepreneur has achieved so many career milestones in his 44 years of life that it's hard to believe they've all happened to the same person. In advance of Tesla's grand reveal of the Model 3--the electric car Musk hopes will change the auto industry forever--here are seven of the biggest moments of his career so far.

1. Compaq buys Zip2.

In 1999, four years after starting newspaper software company Zip2, Musk sold the company to Compaq for $307 million--the largest sum ever for an Internet company at the time--netting him $22 million. Musk was just 24 when he founded the company, having dropped out of his Stanford applied physics and materials science Ph.D. program after two days to become an entrepreneur.  

2. Musk starts an e-payment revolution.

With $10 million he earned from the sale of Zip2, Musk co-founded e-payment company X.com with hopes of building a full-service, online financial services company. After a merger with competitor Confinity, X.com's board ousted Musk and renamed the company PayPal. In 2002, eBay purchased PayPal for $1.5 billion, pocketing Musk a cool $180 million.

3. Accelerating vehicle technology.

In 2003, Musk embarked on a mission to bring electric cars to the masses by co-founding Tesla Motors. He bankrolled the company himself at first, turning away early-stage investors to preserve his status as majority owner. In addition to the forthcoming Model 3, Tesla's electric car models include the Roadster, the Model S, and the Model X.

4. Shifting to solar.

In 2006, Musk invested $10 million in solar technology company SolarCity and became its chairman. By reducing inefficiencies in the solar panel installation industry, Musk hopes to do for solar energy what Dell did for PCs. His ultimate goal is global adoption of solar technology.

5. Fourth time's the charm.

After three failed test launches for the private rocket ship company SpaceX, Musk used his remaining resources of the company to fund a fourth flight, which made history in 2008 for being the first commercial spacecraft to successfully orbit Earth.  

6. Partnering with NASA.

Two days before Christmas in 2008, NASA awarded SpaceX a $1.6 billion contract to fly 12 flights of SpaceX's Falcon 9 carrying the Dragon spacecraft to the International Space Station. The agreement represented NASA's first contracted cargo delivery flights to space.

7. Introducing the Hyperloop.

In 2013, Musk published a white paper outlining his 800-mile-per-hour transportation tube concept called the Hyperloop. Musk claimed the system could transport passengers from San Francisco to Los Angeles in half an hour. Two Los Angeles-based startups currently working to make the concept a reality are Hyperloop Transportation Technologies and competitor Hyperloop Technologies.