Chanel and the Ballets Russes. Halston and Martha Graham. Geoffrey Beene and Twyla Tharp. The fashion greats who’ve designed for dance make a long list. But how did classical ballet and modern dance influence fashion? This groundbreaking show is the first to ask—and answer—the question. Among its treasures: Anna Pavlova’s tutu for The Dying Swan (flown in from Russia), and tutus and couture worn by Margot Fonteyn. —L.J.