Some rocket manufacturers have taken to 3-D printing certain components of their spacecraft. Relativity Space wants to print the whole thing. Co-founders Tim Ellis and Jordan Noone, college friends who got their start with rocketry in USC's Rocket Propulsion Lab, founded the startup in late 2015. They cold emailed Mark Cuban, who soon agreed to fund the startup's seed round. Relativity has since 3-D printed a functioning rocket engine consisting of just three parts--compared with the 2,700 components that make up a traditional one. Printing such large parts drastically cuts down on time and labor, which will allow the company to charge less and run more frequent trips to space. It's targeting a customer base of midsize satellite companies and already has $1 billion in contract commitments. In March, it inked a deal with NASA to use the Stennis Space Center in Mississippi for rocket tests. The co-founders hope to begin flights by 2020. "Looking forward 50 years," Ellis says, "I can't see a future where things that fly are not entirely 3-D printed." --Kevin J. Ryan

In 2014, Krisna Bhargava was getting his PhD in material science from the University of Southern California when he realized he could build better tools to conduct medical tests to be used in doctors' offices and emergency rooms. "Running medical tests is like cooking--it's all done by hand," says Bhargava. "If you go to the hospital and think you have influenza or pneumonia, a test will take a day or two. But doctors, and patients, need results in an hour." While studying microfluidics and 3-D printing, he found that he could take the testing lab and shrink it to the size of a shoebox and still conduct 30,000 different medical tests. A year later, Bhargava sought out reinforcements. He tapped Bryant Thompson, who was a master's student intern at the time, along with his adviser Noah Malmstadt, and Richard Roberts, the chair of his department at USC. In time, they'd launch ReoLab. The company has raised just under $1 million and plans to raise several million more in a Series A to fund clinical trials. By 2020, Bhargava says the company will be on the market--selling a shoebox-size lab for about $1,000 and an annual subscription plan for the testing pods. "We want it to be stupid easy, like a Keurig machine for diagnostic tests," says Bhargava. --Will Yakowicz

When Rip Pruisken and Marco De Leon started testing recipes for their Amsterdam-style stroopwafels (thin waffles with sweet flavoring), they were students living in Brown University's dorm and often blew out the power in the building with their industrial press. Pruisken kept the machine--made of two 15-pound cast-iron plates--in his room so the co-founders could tinker with the ingredients and sample them with friends. "The irons are really hot, so I've lost a lot of the sensation in my fingertips," says Pruisken, who grew up eating stroopwafels in Amsterdam. "I guess that's a good thing when I hold a hot cup of coffee."

Now, the co-founders are making their Rip Van Wafels in a proper facility and have raised $3.8 million from private investors to grow their Brooklyn-based company. And thanks to a key deal with Starbucks in 2016, Rip Van's revenue jumped 76 percent by the next year. The company's waffles come in eight flavors, including chocolate brownie, vanilla, and strawberry. What's more, the products are low in sugar and made from natural ingredients--two factors that Pruisken and De Leon value. The co-founders plan on expanding to other packaged food projects in the next two years. --Emily Canal

Kevin Gelfand and Martin Reiman, both 28, met when they pledged the same fraternity in college, and back then, they didn’t expect to start a company together. But they saw a need for affordable, quick, and healthy foods on college campuses and in 2011, during their junior year, they launched Shake Smart at their school, San Diego State University. "The gym is definitely one of the most popular areas on campus, but the food options never really matched that," Reiman says. "We would exist off [pre-made] protein drinks for most of our time there and most of them are awful--that was never really a great experience." Their San Diego-based startup makes and sells protein shakes, sandwiches, wraps, acai bowls, and cold brew coffee, all for between $3 and $7. Customers use the company’s proprietary self-order system, which keeps hiring costs low and ensures that menu prices fit within the budget of most college students. Last year, the company saw more than $3.6 million in revenue, expanded to 10 restaurants on campuses in California, Texas, and Florida, and employed more than 150 people. The co-founders raised nearly $1.5 million in total funding from friends and family, personal savings, and loans. --Emily Canal