He was a Belgian sculptor and painter, naturalized French, member of the Cobra group and the Zero Group. As a painter he worked with very different techniques, from painting on fabric to mobile planes and games of light, after which he dedicated himself to Cinétisations, or deformations of photographic images with an optical effect of movement. Finally he concentrated on dynamic sculptures, and became the major exponent of kinetic art, famous for his monumental fountains, moved by the movement of water: the most important at Palais Royale in Paris, as well as on Bd du Roi Albert II in Brussels and at the Fondation Maeght in St Paul de Vence (F).