How did Piet Mondrian’s art inspire Alexander Calder to make abstract art?

In late 1930, Alexander Calder visited the studio of Dutch painter Piet Mondrian, an encounter that proved to be a pivotal turning point in his career. Calder described this visit as a "shock" that propelled him toward abstract art.1

Inspired by Mondrian’s signature geometric compositions, Calder suggested that it would be interesting to make the painter's static rectangles oscillate. This idea sparked Calder’s transition from his earlier figurative wire sculptures toward experiments with motion. Following this experience, he began creating works that incorporated mechanical movement, such as Small Sphere and Heavy Sphere (1932–33), and eventually developed his iconic mobiles—balanced, kinetic sculptures that model three-dimensional forms as they move through space.1