Alexander Calder was one of the leading US-American artists of Classic Modernism. His major work must be classified as Kinetic Art; Marcel Duchamp called Calder's sculptures which move in response to air currents 'mobiles', while Hans (Jean) Arp called Calder's stationary sculptures 'stabiles'. Besides, Calder developed a miniature circus with little figurines and mechanical animals. His lifelong friendship with Joan Miró and their constructive artistic exchange was reflected in the works of both artists. Since 1987, Calder's estate has been held by the Calder Foundation in New York.