Bill Gates has invested millions in these Silicon Valley startups over the past decade

EtaGen is a startup producing ultra-efficient generators that supply power for companies, buildings, and microgrids. In 2012, CEO Shannon Miller told MIT Tech Review that EtaGen's engines use on average 25% less fuel (like natural gas or diesel) than traditional gas-powered generators.

Founded in 2010, the company has raised $133 million to date. Bill Gates and others invested $83 million in a Series C funding round in early 2018.

With over 150 million users in 196 countries, Change.org is a popular site where people can start petitions for specific causes. Current US-based petitions include one to strengthen gun laws and one supporting farmworkers' rights.

In a Series C funding round in 2014, Change.org received $30 million from Gates and others. The company has raised $83 million to date.

Founded in 2002, Varentec develops products for electrical grid systems, including a software platform that lets cities more easily manage how power flows. The startup claims that its devices can help utility operators reduce wasted voltage, manage peak power demands, and avoid overloading circuits.

Gates participated in two separate funding rounds in 2014 and 2015. To date, the company has attracted $41.9 million in venture capital.

Since its founding in 2011, Impossible Foods has been on a mission to engineer plant-based "meat" that tastes like the real thing. The meat-like flavor largely comes from an ingredient called heme, which allows the Impossible Burger to "bleed" like a beef burger.

In April, the food-tech startup debuted its sliders at 140 White Castle locations across New York, New Jersey, and Illinois, and its burger is now available at over 1,400 restaurants nationwide.

Impossible Foods has raised an estimated $387.5 million to date, with Bill Gates participating in three funding rounds that totaled $208 million from 2013 to 2017.

Gates has also invested in another plant-based food startup, headquartered in Los Angeles, called Beyond Meat in 2015. The Series E funding round totaled $17 million.

Memphis Meats has a similar goal to Impossible Foods, but it's aiming to achieve it in a different way. Instead of relying on plant-based ingredients, the company is working to cultivate meat from animal cells in a lab. So far, Memphis Meats has made lab-grown chicken strips, lab-grown meatballs, and lab-grown duck.

The team previously told Business Insider that it expects to reduce production costs over the next few years, and start offering its products to the public in 2021.

In 2017, Gates participated in a $17 million Series A funding round.