Three years ago, Eben Upton needed a cool gadget to lure students to his computer science program at the University of Cambridge. So he invented the Rasberry Pi. It has since become the cheapest hackable computer on the planet. He has sold five million (at $20 to $35 a pop), released a faster version this February, and become an icon of DIY culture. Now, as Microsoft prepares to launch a Pi-friendly version of Windows, Upton is bracing for a wave of new users. He recently spoke with Popular Science about hacking, education, and his tiny creation.