It describes how two people who lost use of their arms and legs because of strokes years before were able to control free-standing robotic arms with the help of a tiny sensor implanted in their brains. The sensor, about the size of a baby aspirin, eavesdropped on the electrical activity of a few dozen brain cells as the study participants imagined moving their arms. The chip then sent signals to a computer, which translated them into commands to the robotic arms. The chip, implanted in the motor cortex, could make life far easier for countless people around the world. It will still take about another 5-6 years to perfect and simplify the technology, say researchers. In the meantime, we can all enjoy watching Ms. Hutchinson do something on her own for the first time in over a decade (see video below). "You could see an enormous grin when she managed it," researcher John Donoghue from Brown said.