Alexander "Sandy" Calder was born into a family of renowned artists who encouraged him to create from a very young age. As a boy, he had his own workshop where he made toys for himself and his sister. He received a degree in mechanical engineering in 1919 but soon after decided to pursue a career as an artist. Calder attended classes at the Art Students League in New York from 1923 to 1926, supporting himself by working as an illustrator. In 1926 Calder arrived in Paris where he developed his Cirque Calder,a work of performance art employing small-scale circus figures he sculpted from wire, wood, cloth, and other materials. Through these elaborate performances, Calder met members of the Parisian avant-garde. At the same time, Calder sculpted three-dimensional figurative works using continuous lengths of wire, which critics described as drawings in space. He explored ways to sculpt volume without mass and to captured the essence of his subject through an economy of line and articulated movement. Calder's wire works then became increasingly gestural, implying motion. By the end of 1930, this direction yielded his first purely abstract sculptures. After translating drawing into three dimensions, Calder envisioned putting paintings into motion. He developed constructions of abstract shapes that can shift and change the composition as the elements respond to air currents. These sculptures of wire and sheet metal (or other materials) are called "mobiles." A mobile laid flat exists only as a skeleton, a reminder of its possibilities, but when suspended it seems to come alive. Calder also developed "stabiles," static sculptures that suggest volume in multiple flat planes, as well as standing mobiles, in which a mobile is balanced on top of a stabile. Calder furthered his work by developing a monumental scale. His later objects were huge sculptures of arching lines and graceful abstract shapes that now inhabit public plazas worldwide. Calder was an artist of great originality who defined volume without mass and incorporated movement and time in art. His inventions redefined certain basic principles of sculpture and have established him as the most innovative sculptor of the twentieth century.