Here are 18 things Elon Musk has invested in - the good, the bad, and the ugly

Musk was 24 when he dropped out of graduate school for physics at Stanford University to launch his first company, Zip2 Corporation — a dot-com media company that supplied maps and business directories to online newspapers.

He linked digital online maps from Navteq to a business directory and created the internet's first online Yellow Pages.

Four years later, in 1999, Musk sold the company to computer-manufacturer Compaq for $307 million. At that time, it was the largest amount ever paid for an internet company.

The same year Musk sold Zip2, he used $10 million from the sale to found the online financial-services company X.com.

Musk wanted to focus on the new technology of making payments via email, so he merged his company with a competitor called Confinity — which started the online money transfer process PayPal.

In a heated clash of personalities and egos, however, the cofounders of Confinity fired Musk from the board, then renamed the company PayPal.

The online auction company eBay purchased PayPal in 2002 for $1.5 billion.

Cofounded in 1998 by Musk's cousin, Lyndon Rive, Everdream sold desktop management services to small businesses. It also managed and fixed antivirus software, performed data backups, and administered data encryption.

Musk, who was still involved with PayPal at the time, invested in Everdream on the fourth round, according to the Silicon Valley Business Journal.

Rive and his twin brother, Russ, sold the company, headquartered in Fremont, California, to Dell in 2007.

In an interview with Inc., Musk explained why this project was one of the most important things to happen on Earth since its birth 4.5 billion years ago:

"There was the advent of single-celled life, multicelled life, the development of plants, then animals," he said in the article. "On this time scale, I'd put the extension of life to another planet slightly above the transition from life in the oceans to life on land."

To that end in 2002, Musk founded SpaceX, an aerospace manufacturer in Hawthorne, California, with the goal of making rockets more affordable.

SpaceX's Dragon spacecraft became the first commercial spacecraft to shuttle cargo between the International Space Station and Earth in 2012. Musk eventually wants to send humans to space in the Dragon capsule and has plans to send humans to colonize Mars.

He teased his Martian ambitions on Instagram in September 2015, but has said he will describe them in detail in late 2015.

The Musk Foundation's goal is award grants that support research into renewable energy, space exploration, education in science and engineering, and childhood diseases and disorders.

According to Inside Philanthropy, the foundation has given out a total of $783,700, including a donation of $250,000 to build a solar-power system in Soma City, in the Fukushima prefecture of Japan, following the tsunami disaster there in 2011.

Given the foundation's bold ambitions, its low-tech website is pretty hilarious.

After investing heavily in Tesla Motors, founded by Martin Eberhard and Marc Tarpenning in 2003, Musk joined the company's board of directors.

Its first car, the Roadster, wowed consumers with its sports-car-like ability to accelerate from 0 to 60 mph in under four seconds and travel about 250 miles on a single charge.

After the 2008 market collapse, Musk took a more active role and became CEO of the company, a position he still holds today.

Their latest car is so good it broke the Consumer Reports rating system.

Musk reportedly purchased a 10% stake in this small-satellite provider in early 2005, which "will give SpaceX a window on the thinking of the world's most successful vendor of small, inexpensive spacecraft and ultimately could provide business for SpaceX," according to Space News.

Surrey Satellite Technology got its start building amateur radio satellites, and now builds, launches, and operates small spacecraft for weather monitoring, communications, and other purposes.

Musk has been a longtime proponent of sustainable and green technology.

In keeping with the energy-saving ilk of Tesla, he invested heavily in SolarCity — one of the country's largest installers of home solar panels — which was founded in 2006 by his cousins Lyndon and Peter Rive. He now acts as chairman of the company.

SolarCity designs and installs solar-powered clean-energy systems. It also audits and builds electric vehicle charging stations. In April 2015, it announced a partnership to incorporate Tesla batteries into a solar-battery backup system.

According to Crunchbase, Musk invested in Mahalo when the site was founded in 2007.

Mahalo is like Wikipedia, Ask Jeeves, and Quora all on one website. The site allows people to post and answer questions.

After Google overhauled its search function, however, the company was forced to lay off 10% of its staff in 2011. It has since shifted its strategy to create original how-to videos, plus live, user-generated question-and-answer sessions.

Musk did a series of videos with the website in 2011.

Musk is no longer invested in PayPal, but he is invested in one of its biggest competitors: an online payment startup called Stripe.

The company aims to allow online apps and companies like Lyft and Facebook to accept payments from anyone anywhere.

It was recently valued at $5 billion. It also has a new partnership with Twitter that adds "buy" buttons to tweets.

This ambitious, future-oriented genetics biotechnology startup was founded by brothers William and Michael Andregg in 2008 with the goal of unlocking the biggest secrets hidden in DNA.

The company said in 2009 that it wanted to "sequence 100% complete human genome" in less than 10 minutes for less than $100, according to Gigaom.

But with many companies competing with the fastest and cheapest DNA sequencing technologies, according to Fierce Biotech, the company shut its doors in 2012.

Musk donated $1 million in funding to a new science museum — spearheaded by webcomic The Oatmeal — dedicated to Nikola Tesla, one of "history's most important inventors," in 2014.

The center is in Wardenclyffe, New York — the same place Tesla built a giant transmitter tower to experiment with sending messages and shuttling wireless electricity.

Musk is even going to build a Tesla Supercharger station — the world's quickest charging station — in the science center's parking lot.

Musk doesn't trust artificial intelligence. In fact, he likened it to "summoning the devil" at MIT's annual AeroAstra Centennial Symposium in late 2014.

It makes sense, though, that Musk has invested in a number of leading AI companies that are researching how to make future smart bots more friendly.

One of these companies is AI startup Vicarious, founded in 2010. Musk contributed to a $40 million investment in Vicarious in spring 2014.

Though this company has been unusually secretive, it's "building a unified algorithmic architecture to achieve human-level intelligence in vision, language, and motor control," according to Vicarious' website.

Vicarious founder Scott Phoenix told The Wall Street Journal that the goal is to "have a computer that thinks like a person, except it doesn't need to eat or sleep."

In a CNBC newscast, Musk says that his investments in AI technology companies are "not from the standpoint of actually trying to make any investment return … I like to just keep an eye on what's going on with artificial intelligence. I think there is potentially a dangerous outcome there."

"There have been movies about this, you know, like 'Terminator,'" Musk continued, according to The Guardian. "There are some scary outcomes. And we should try to make sure the outcomes are good, not bad."

Hence, his high-profile investments in an AI company like DeepMind, founded in 2011 and later acquired by Google in 2014, at which time it was renamed Google DeepMind.

The company's goal is to "solve intelligence" by melding machine learning and neuroscience into powerful, all-purpose computer algorithms.

In January 2015, Musk donated $10 million to the Future of Life Institute, which supports research in mitigating risks associated with developing human-like AI.

Some projects involve creating ethical rules and systems for AI while others focus on keeping AI-powered weapons under control.

The organization holds public competitions to encourage technological inventions that will benefit humanity.

Their categories are diverse and promise cash awards for advancements in sustainable fishing, asteroid deflection, invisibility cloaks, and synthetic astrobiology.

Current prizes include the $30 million Google Lunar XPrize, to land a privately funded robot on the moon, and the $2 million Wendy Schmidt Ocean Health XPrize, to help restore ocean ecosystems.

Musk is a member of this foundation's board of trustees.

Launched in 2007, NeuroVigil developed the world's first portable brain monitor, the iBrain. Musk became a principle investor of the company in May 2015.

NeuroVigil focuses on analyzing electrical signals from the brain to help drug companies conduct clinical trials as well as diagnose and treat patients with neurological and neurodegenerative diseases.

It also wants to help NASA keep track of the brains of astronauts while they're aboard the International Space Station.

Back in 2013, Musk used SpaceX to publicly announce his concept for making high-speed travel a reality: the Hyperloop. At the same time, he made his research and ideas open-source.

The Hyperloop is a proposed rail system that would ferry people in capsules through tubes at speeds exceeding 500 mph. Musk initially pitched it as a quick, safe, and energy-efficient way to travel between San Francisco and Los Angeles.

Musk and SpaceX announced that they aren't planning on commercializing this technology, though Motherboard has reported otherwise.

Several private companies, such as this LA-based company, are working on commercializing the technology.

Musk has been compared to some of our greatest visionaries, including late Apple CEO Steve Jobs, and has been described by a former coworker as "brilliant, dynamic, charismatic" and "an exceptional freak of nature."

He changed the way we use the internet, has devised innovative solutions to environmental and sustainability challenges, and has helped fund projects that tap the brightest minds for the betterment of society.

Despite only allowing himself to take a strict six hours of sleep every night and working a reported 100-hour work week, it's unlikely that Musk will accomplish everything on his hefty to-do list by the end of his lifetime.

But who knows? Perhaps that won't even matter if we're all shipped off to Mars by then.

If you know of any other companies that Musk is involved in that are not listed here, send us an email.