Elon Musk, aka the "real life Tony Stark," is a self-made billionaire engineer, scientific visionary and investor who has managed to capture the imaginations of the science, tech and finance communities simultaneously. Musk serves as CEO of two huge enterprises, Tesla Motors, Inc. (NASDAQ: TSLA) and SpaceX, and is he chairman of SolarCity Corporation (NASDAQ: SCTY), although a sizable portion of his fortune was built on 20-plus years of selling or taking his other companies public.

In 1999, Musk sold his first company to Compaq for $307 million. He sank $10 million into X.com, which became PayPal Holdings, Inc, (NASDAQ: PYPL), and was purchased by eBay in 2002 for $1.5 billion. He became an investor in Everdream Corporation in 1998 before Dell acquired it in 2007. Similarly, Musk invested in the artificial intelligence company DeepMind Technology prior to a 2014 buyout by Google.

Entering 2016, Musk's personal investments were spread across technology, science, exploration and real estate assets. Prior to becoming CEO, Musk invested heavily in electric car producer Tesla, and according to research company FactSet, Tesla remains his largest holding at approximately $6 billion. He owns roughly 20% of SolarCity stock valued at around $575 million by the end of 2015. He is an owner of SpaceX.

The first two months of 2016 stung Musk's public portfolio, as Tesla and SolarCity lost $3.5 billion between Dec. 31, 2015, and Feb. 10, 2016. According to S&P Global Market Intelligence, SolarCity was the worse performer at -63%, though most of Musk's losses occurred with Tesla at -40%.

Tesla

Elon Musk is Tesla's largest investor, controlling more than one-fifth of total outstanding shares. Musk was an original founder of the firm in 2003, though he took a much more active role following a disastrous 2007 when the company reduced its workforce by 10%. He was named CEO in October 2008. Two months later, the company used an emergency seed round of financing to avoid bankruptcy. Through the next five-plus years, Tesla's stock skyrocketed and earned Musk billions.

Musk remains optimistic about Tesla despite the early-2016 struggles. On Feb. 12, 2015, Musk informed analysts during an earnings call that Tesla would boast a market capitalization that "would be basically the same as Apple's is today" by 2025. In the week between Feb. 10 and Feb. 17, 2016, Apple's market capitalization hovered around $530 billion; Tesla's was less than $25 billion.

SolarCity

While Musk has been more bullish on Tesla since 2013, he has been more relaxed about SolarCity. In 2013, for example, his portfolio was approximately 72.4% in TSLA to 27.6% in SCTY. The ratio changed to 85% in TSLA and 15% in SCTY by the following year. In 2015, the divergence became more extreme as TSLA made up 91.6% to just 8.4% for SCTY, according to FactSet.

SolarCity's day-to-day operations are largely run by Lyndon Rive, Musk's cousin. Musk helped Rive launch the company in 2006. SolarCity prices traded as high as $86 per share in February 2014 but collapsed to just under $20 per share two years later.

SpaceX

Elon Musk is the majority owner of SpaceX, a private company valued at about $12 billion in a January 2015 round of financing. Outside of his public investments, SpaceX is the largest item in Musk's personal portfolio. The company relies heavily on government subsidies and contracts with NASA to remain viable, according to a 2015 report from the LA Times.

SpaceX has already created and launched the first private spacecraft to reach the International Space Station, and Musk hopes to have a colony on Mars by 2040, filled with 80,000 colonists. The project is loosely associated with his more recent Hyperloop project, a proposed high-speed transport rail system between Los Angeles and San Francisco; the project relies on engineers from SpaceX.

Property

According to MarketWatch, Musk owned three properties valued at more than $27 million in October 2015. The three properties have a combined 26,081 square feet, the vast majority of which belongs to his Bel Air primary residence.

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