Kinetic art takes movement as its true material: sculptures that swing, rotate or vibrate, and works whose meaning only unfolds as the viewer walks around them. The idea stretches back to Futurist and Dada experiments - Duchamp's Bicycle Wheel (1913) and Naum Gabo's motor-driven Standing Wave (1919-1920) - but the movement crystallized at the 1955 Paris exhibition Le Mouvement at Galerie Denise René, which brought Calder, Tinguely, Agam and Soto under one kinetic banner. Through the 1950s and 1960s it branched into motorized junk machines, delicate air-driven mobiles, vibrating rods and moiré constructions, and it crossed freely with Op art. By treating time, chance and the spectator's own body as artistic materials, kinetic art broke with the static object more radically than any movement before it.