While visiting the studio of Piet Mondrian, known for his rigorous geometric abstractions, Calder noticed some rectangular pieces of cardboard attached to the wall. What would happen if these shapes were to move? Calder’s mobiles emerged from these musings. These mobiles take diverse forms, and The Monster is one of the floor-standing type. Triangular or circular sheets of steel are attached to each end of the suspended rods, and changes in balance generate movement. Calder realized that such movement imbues what had been an inorganic object with a sense of life.