Over more than fifty years, Alexander Calder (1898-1976) explored how opposing elements and forces could attain symbiosis in his sculptures. Though he noted that "anything suggestive of symmetry is decidedly undesirable," the interactions of shapes, colors, sound, and movement in his work never fail to strike a harmonic balance. His creations appear whimsical, yet they are carefully calibrated and composed. Calder eschewed traditional materials in favor of wire, sheet metal, and wood to realize these dynamic sculptures. Both his bent wires floating in midair and his abutted and torqued metal panels encapsulate voids, playing positive forms against negative space. The artist often limited his palette to the "most disparate colors"-black and white--but even seemingly simple, monochromatic works continuously evolve: cutouts reveal new shapes as they twist around invisible cores, and their shadows flicker in concert. Calder did sometimes punctuate his sculptures with other colors, using red, yellow, and blue to suggest movement, add tension, and redirect the eye. Designed to unfold in space and time, many of Calder's artworks include an element of unpredictability. Even early sculptures with precisely prescribed motion contain surprises, such as the gentle whir emitted by the gravity-defying discs of Quattro Pendulati. Gongs, dings, hums, and silent pauses add humor and sound to enliven his abstractions and bring their contrasting components together as cohesive reflections of the surrounding world.