In 2007, Bre Pettis, an artist and former schoolteacher, co-founded the hackerspace NYC Resistor. Its members wanted a 3D printer, but the technology, which had been around since the 1980s, was expensive and its application, almost exclusively industrial. A few hackers started working with open-source designs. Pettis partnered with two of them, and they debuted their first consumer product, the CupCake CNC, in 2009. The invention became a business, MakerBot Industries, which Pettis sold four years later for around $400 million. He's now on to his next project, Bold Machines, a 3D-printing workshop that helps artists and entrepreneurs transition quickly from rough ideas to working prototypes. "We basically accelerate the future," Pettis says.