Christos Porios , 16, lives in Alexandroupolis, a small Greek city on the Aegean Sea about 20 miles from Greece's eastern border with Turkey. "My mother's a teacher and my father's a mechanic," he explains, adding that neither is particularly knowledgeable about computers—especially compared with him. For years, he's had free rein over the family PC, and he's taken advantage of the time to teach himself programming. Mainly, he uses sites like Wikipedia, YouTube, and the Khan Academy—a portal with thousands of short, free educational videos. "Yes," says Porios. "I would call myself a geek." "At first they were like, 'You can't learn anything that way.' But they saw I was getting serious. I was learning stuff, and I liked it. They realized that 'real life' includes things like machine learning." Last fall, as the Greek economy spiraled toward default and rioters filled the streets of Athens, Porios was g...