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. How do artists respond to a world in flux? In what ways do artists act as agents of change, and what kinds of aesthetic choices do they make? Chinese artist Ai Weiwei, American photographer Catherine Opie and Ghanaian sculptor El Anatsui bear witness, through their work, to transformation – cultural, material and aesthetic – and actively engage communities as collaborators and subjects.