The researchers’ theory helps to explain the wrinkles that form on the skin of an apple as its flesh shrinks. Sheet wrinkle experts Lakshminarayanan Mahadevan, a mathematician at Harvard University, and Enrique Cerda Villablanca, a physicist at the Universidad de Santiago de Chile, are sharing the prize in physics. The theory also offers some insight into the wrinkles that form on people’s skin, although it can’t predict how many wrinkles any one person will get.