A microrobot, fully integrated with sensors and a computer, small enough to balance on the ridge of a fingerprint. Credit: Marc Miskin, University of Pennsylvania (Inset: A microrobot on a US penny, showing scale. Credit: Michael Simari, University of Michigan) Researchers at the University of Pennsylvania and the University of Michigan have built the smallest fully programmable autonomous robots ever created. These microscopic machines can swim through liquid, sense their surroundings, respond