Ten years ago, Dutch scientist-turned-artist Theo Jansen had a vision: art that evolved. The evolution of his bizarre machines that walk when powered by gusts of wind took place on a computer. Trained as a physicist (he was a doctoral student but did not finish), Jansen designed a program that simulated pairs of legs of different lengths. He then created virtual creatures and raced them against each other to find the ones that moved most efficiently. These he built, and he hopes one day to find a way to let them evolve on their own. In the meantime, he is working on ways to keep them moving even after the wind dies down. Their legs are comprised of pistons inside a tube, connected to a crankshaft. Once a gust of wind gets the sculpture going (most have polystyrene windmill blades or sails to give them a boost) and the pistons start moving, the legs could function as pumps and store compressed air. The critter could then burn that stored energy to keep puttering along regardless of the weather. "It's like giving it muscles," says Jansen with delight.