Aristides is a typical 13-year-old boy. He plays basketball after school, is learning the clarinet, and in the evening sits in front of his computer playing games. There is one game that he is especially keen on, however, which marks him out from his peers. Every day he logs on to www.fold.it, where, under the nickname “Cheese”, he plays a game that involves twisting, pulling and wiggling a 3D structure that looks a bit like a tree’s root system. He manipulates different lengths of these snaking green tubes until they fit into the smallest volume possible. It may sound like a rather bizarre game – a distant 3D relative of Tetris, perhaps – but it is in fact a brilliant disguise for one of the toughest conundrums facing biologists today: how do proteins fold?