Alexander Calder (1898–1976) is one the the most influential sculptures of the 20th century. Using innovative (especially at the time) materials like sheet and wire steel he invented the "mobile" - kinetic works of art that play off each other and change aesthetics when they move, "stabiles" - static pieces, usually of monumental size, free-standing off the ground. As a major contributor to abstract art, he enjoyed the effects of shapes and color (often using a bold red later coined as "Calder red") on open space.
After getting a degree in mechanical engineering he had his first one-man show in New York and then traveled to Paris where he created his circus series made of wire, wood, glass and cloth. From working small-scale, he started getting bigger and more abstract with his creations, eventually making pieces like "Flamingo" in Chicago.
Perhaps what started it all was: jewelry! At the age of 6, Calder was making jewelry for his sisters dolls and started carrying pliers and wire around with him everywhere. As he once put it "I think best in wire". Fabricating 1,800 unique pieces by hand during his life, his jewelry became quite popular with artists, collectors, performers, etc. For example, in 1942, Peggy Guggenheim wore one Calder earring and one by Yves Tanguy to the opening of her New York gallery, The Art of This Century, to demonstrate her equal loyalty to Surrealist and Abstract art, examples of which she displayed in separate galleries. Again, using revolutionary materials for time time: steel wire, brass, wood, and "gems" made from broken glass and porcelain, Calder is thought to have started many trends that became popular in the 60's and 70's in the 40's.