Doctors have long dreamed of delivering drugs to specific parts of your body, and they may soon have a clever way to do it: fish. UC San Diego researchers have developed nanoscale metallic fish (they're just 800 nanometers long) that could carry medicine into the deeper reaches of your bloodstream. Each critter has a gold head and tailfin, as well as a nickel body joined by silver hinges. You only have to subject them to an oscillating magnetic field to make them swim -- there's no need for propellers or a passive (read: slow) delivery system. That, in turn, could make the drug carriers smaller even as they move quickly.