Without a second's hesitation, Vladimir Tenev will tell you the first time he invested in the stock market. He was just 12 but bullish on Palm, the maker of the PalmPilot, a hunch that earned him $1,000. That enthusiasm for mobile tech and the stock market led him to Robinhood, Tenev's startup, co-founded with Baiju Bhatt in 2013. Robinhood is a commission-free brokerage that lets you trade from a smartphone app. "If you're someone who's in your late teens or early 20s and you want to invest a hundred bucks to try it out for the first time, it [used to be] cost prohibitive," Tenev says. He's lured in enough young users to force older rivals like E-Trade and Charles Schwab to cut fees--the same way those firms forced Wall Street wirehouse firms such as Merrill Lynch to reprice trades. The company is focused on making money by providing premium features to its heavy-duty users through a $10 per month subscription service called Robinhood Gold. -Salvador Rodriguez

At the center of the booming commercial universe known as New Space is an emerging generation of satellites that are much smaller than the floating dinosaurs they're designed to replace. Smaller satellites need even smaller propulsion systems, and Accion Systems makes very small ones indeed. "The key to our technology is a chip the size of a penny," says Louis Perna, co-founder and lead mechanical engineer. "We can help small satellites stay in space longer, get to where you want them to be, and maintain that location." These chips are also inexpensive and uncomplicated. They're deployable in arrays like so many postage stamps, suitable for smallsats (which are about the size of dorm fridges) and cubesats (more like whiskey-bottle boxes). You want bigger than that? No problem. The chips are scalable for satellites of any size. Powered by charged particles that accelerate to enormous speeds, the tech enables the satellites to carry out their missions once they've been launched into space. Yes, this is rocket science: Co-founders Perna and Natalya Bailey are both rocket scientists. They developed the technology while working on their PhDs at MIT. The name of the company, which had $4.5 million in sales last year, comes from Accio, the summoning charm Hermione Granger taught Harry Potter at Hogwarts. -David Whitford

WHY WE'RE A BEST PLACE TO WORK

Cadre refers to a special group of people who work together for a common goal. That's how we see our business. Our founding principle is that we are stronger together, especially when we bring in a team with diverse backgrounds and experiences. The real estate industry may be resistant to change, but Cadre works hard to deliver its clients the opportunity to invest in quality real estate. We strive to find fearlessness, selflessness, and commitment to being exceptional in all our new hires.

Lots of companies have made consumer products for experiencing virtual reality. With Lucid VR, Han Jin has created a simple way to capture it. The company's $499 LucidCam, set to ship in June, is among the first virtual reality cameras geared toward the average consumer. It uses two eyes to take in the world, in much the way humans do, and then converts those images into three-dimensional photos or video that can be viewed through Google Cardboard or Lucid's $30 phone case. The smartphone-size LucidCam can be strapped to a filmer's chest to act like a GoPro. Its video and image files are small enough to be easily shared, and the system supports live streaming over Wi-Fi. Jin, who co-founded the company with Adam Rowell, uses LucidCam as a way to stay in touch with his family back in Germany and China. "Sharing experiences through normal pictures is great, but it doesn't really show them how I'm living life," Jin says. "This is the closest you'll get to feeling like you're right there with somebody." --Kevin J. Ryan

Web video is the medium of the moment. And Karen X. Cheng is the kind of talent who seems made for it. She's a one-woman creative agency, known as Karen X, who writes and directs viral videos for brands as varied as Beats and Credit Karma. Her videos have attracted millions of hits. Did she ever expect to get into this line of work? "No, absolutely freaking not!" Cheng says. In 2012, she announced her resignation from Microsoft by writing lyrics about her team, performed as a parody of Don McClean's "American Pie," which she posted on YouTube. After TechCrunch got hold of it, the video went viral. These days, Karen X is a boutique marketing firm that offers both consulting and video creation services. Being a solo entrepreneur doesn't mean that Cheng works alone. She marshals a slew of creative contractors, including video editors, lighting directors, storyboard artists, composers, and PR researchers. "I'm able to access a level of talent that I couldn't if I were hiring full time," Cheng says. --Sonya Mann