Students use Tilt, a Kickstarter-meets-Venmo payments app, to organize frat parties and weekend trips, inviting all of their friends to chip in and spreading the app to new campuses. In the past year, the company has grown by 41 percent every month on college campuses, and 350 percent by the number of projects funded. The San Francisco-based startup is betting that this viral demand will help it graduate along with its fiercely loyal users, turning the platform into the next Facebook or Snapchat. Co-founder James Beshara, a Texan whose post-college nonprofit job turned into a stint as a South African debt collector, soon learned how to adapt to a changing market. He started Tilt in Austin as Crowdtilt, a charity-minded crowdfunding platform, but quickly saw the greater demand from young people looking for a better way to send and receive money. "It's meant to be bite-size, simplified, kind of like a Twitter for crowdfunding," he says. Investors are hooked: Tilt has raised some $67.1 million from high-profile backers including Sean Parker, Andreessen Horowitz, Goodwater Capital, and SV Angel.
Note: All data as of 1/31/16

After a harvest, a marijuana grower has to find buyers quickly to move thousands of dollars' worth of fresh product. Most growers have built a network of relationships over the years or work with a pot broker who connects producers and dispensaries. But Tradiv, an online marketplace where growers and retailers can buy and sell legal marijuana on an Amazon-like platform, is replacing the old street-dealer aspects of the marijuana economy. With over 230 businesses using Tradiv in Colorado, about $1 million worth of product is sold each month on the platform, making it as easy for a dispensary owner to buy a pound of high-grade marijuana as it is for a liquor store to buy a case of Scotch. 
Note: All data as of 1/31/16

Jessica O. Matthews recalls that on the night of her aunt's wedding in Lagos, Nigeria, the power suddenly went out. "They brought in a diesel generator to keep the festivities going," she says. "I started to cough and got dizzy." The experience stuck with her and ultimately led her, as a junior at Harvard, to invent Soccket, a soccer ball that captures kinetic energy and stores the power in an internal generator that can light a room or charge a cell phone. Soccket, along with a jump rope called Pulse, generated more than $6 million in revenue last year for Matthews's company, Uncharted Play. The products are typically purchased by governments and large corporations that brand them, and distribute them in Africa, mostly through NGOs. Now, Matthews's wildly ambitious goal is to "democratize on-demand power for everyone" by rebranding her company as M.O.R.E. (motion-based, off-grid, renewable energy), an energy company that's creating a microgenerating system that can harness the kinetic energy of just about anything that moves. On deck: a baby stroller that generates enough power to charge a cell phone.
Note: All data as of 5/23/16

When Colleen Costello was a junior at Rochester Polytechnic Institute in 2011, her grandmother was admitted to the hospital after she slipped and fell. "She was supposed to stay overnight, but the next morning we were told that she had a MRSA infection. She ended up staying for over a week," says Costello. "I naively assumed that people get better when they go into a health care facility." According to the CDC, one in 25 patients gets a health care-associated infection every day. MRSA is a particularly nasty type of infection because its bacteria are resistant to most antibiotics. A biomedical engineering major, Costello approached her friend James Peterson, a mechanical engineering student. Together, they began exploring ways to prevent infection by disinfecting health care facilities (Paterson is no longer with the company). The solution: a new kind of LED white light that disinfects indoor spaces by attacking a molecule specific to bacteria, mold, and fungi. Unlike the disinfecting UV light traditionally used in hospitals, Vital Vio's lights can be left on all the time, because they cause no harm to humans.
Note: All data as of 1/31/16