Alexander Calder was an American sculptor and artist born in 1898 in Pennsylvania. He is known for inventing mobiles, moving sculptures made of weighted objects that are balanced to move freely in response to air currents. Calder made play and movement the major themes of his art over his 50-year career. He created sculptures out of unusual materials like wire, wood, and sheet metal. Some of his most famous mobiles and sculptures include "Mobile", "Devil Fish", "Mercury Fountain", and "Five Swords". Calder had a childlike view of the world that was reflected in his innovative and interactive kinetic artworks.