The Boy With the Lego Hand

Born with a left arm that ends just below his elbow, 9-year-old Aidan Robinson has had his share of prosthetic arms. As a baby, he wore a passive arm, plastic and immovable like a doll’s arm, which trained his brain to develop motor skills equally on both sides. As he grew, he graduated to more complex prostheses.

http://www.theatlantic.com