The fish are just 120 microns long and 30 microns thick, much smaller than a human hair. Researchers can 3D print hundreds of the fish in seconds. The fish are printed with tiny particles of platinum in the tail which react with hydrogen peroxide. When the microfish are placed in peroxide, the tails move, propelling the fish along. The scientists can also add other particles to the materials used to print the fish, including chemicals that can detect and absorb toxins like bee venom.