In a difficult operation, a surgeon moved Kitts’s nerves to different areas of her upper-arm muscles. For months, the nerves grew. Millimeter by millimeter, they moved deeper into then new homes. “At three months I started feeling little tingles and twitches,” she said. A month later, she got her first bionic arm. A research engineer worked with Kitts to make the computer programs match her real movements more and more closely.