Every year in the US, 795,000 people fall victim to stroke, many of them with debilitating effect. Sometimes, the damage affects only a portion of a person’s body, arms or legs, or speech. Often, it renders half of the body useless, limiting the patient’s movement or control. A patient’s rehabilitation usually focuses on improving overall movement of arms and legs. But rehabilitating the extremities—hands and fingers—is often left for a later time.