Alexander Calder (1898-1976) revolutionized the art of sculpture by making movement one of its main components. His invention of the mobile was one of Calder's many achievements. Calder is widely known for his early wire figures as well as his stabiles, static sculptures in sheet metal, which explored the aesthetic possibilities of nontraditional materials. Calder's stabiles and mobiles challenged the prevailing notion of sculpture, proposing a new definition based on the ideas of open space and transparency. His giant stabiles launched a new type of public sculpture, and many have become landmarks in cities around the globe.