The volume documents the profound and transformative impact of Alexander Calder, one of the most revolutionary artists of the 20th century. Calder (1898-1976) in fact changed the way we perceive and interact with sculpture, introducing the fourth dimension of time in art with its legendary mobiles - a term coined by Marcel Duchamp which in French refers to both "motion" and "motive" - and exploring the volumes and voids in the stabiles, his stationary objects, so named by Jean Arp. Over thirty masterpieces made between 1930 and 1960 - Calder's most innovative and prolific years - are brought together in these pages from the earliest abstractions orsphériques to a magnificent selection of /mobiles/, stabiles andstanding mobiles of various sizes, as well as a wide range of Constellations, a term proposed by Duchamp and James Johnson Sweeney for the artist's beloved objects made of wood and wire in 1943, a period when metal was scarce due to the Second World War.