ART21 is an award-winning series of 24 programmes in which 100 contemporary artists talk about their creations, the way they work and their individual view of art. In what ways can art convey equilibrium or disequilibrium? What is reality? How do artists perceive and express it? This episode features the American artist Sarah Sze, English painter Rackstraw Downes and American minimalist Robert Mangold whose works explore the distinctions between balance and imbalance, and demonstrate that the smallest change in a line, a formal element or a structure can be a radical proposition.