DNA origami has been used to build many things on the nanoscale—miniscule doughnuts, teddy bears, even the Mona Lisa. But making a 3D shape is not the same as making a machine—or a robot. Now, scientists have shown they can control a nanoscale DNA arm from the outside world. The technique relies on the negatively charged nature of DNA. In this setup (which is pretty much all DNA), the 25-nanometer arm is made up helices of somewhat rigid double-stranded DNA. It’s attached to a tiny DNA platform through a flexible single strand of DNA. The researchers applied a charge to the system to move the arm around and could track its position using fluorescent signals picked up by microscopy. In some experiments, the arm’s movement was stopped by short DNA strands sticking up perpendicularly from the platform. The arm could only move if the charge was driving it to let go of these complementary strands—and then only to set positions. This demonstrated that the arm could not only spin around, but could also be driven to specific points, the team reports today in Science. And when it moved, it moved fast—each positional change took only milliseconds—1 million times faster than previous DNA nanotechnologies. This controlled movement of a nano-scale robot could be combined with other technologies that allow the DNA to pick up and drop molecules—opening the door to 3D printing materials from the atom up. In addition, an array of these arms could be remotely controlled to manufacture drugs, like a nano-scale roboticized automotive plant for pharmaceuticals.