For scientists working with bacteria in a lab, evolution is a bit of a problem. Bacteria change so rapidly that a cool trait you create one day may be gone the next. Now a researcher reports he may have found a way to solve the problem: a tiny prison for bacteria. It's no bigger than a dime and has six tiny compartments that can each hold a few bacteria. Tiny pipes pump in food, scrub the walls, take out waste, and remove the progeny of dividing bacteria. This keeps bacteria in a kind of holding pattern that means they don't evolve into something different from the one you started with.