Imagine a robot that could help you tidy your home: roving about, sorting stray socks into the laundry and dirty dishes into the dishwasher. While such a practical helper may still be the stuff of science fiction, Caltech scientists have developed an autonomous molecular machine that can perform similar tasks—at the nanoscale. This “robot,” made of a single strand of DNA, can autonomously “walk” around a surface, pick up certain molecules and drop them off in designated locations.