In this preview from the "Art in the Twenty-First Century" Season 6 episode, "Change," artist Ai Weiwei discusses his 2006 work, "Surveillance Camera." "Change" premieres Friday, April 13, 2012 at 9:00 p.m. ET on PBS (check local listings). For more information on Ai Weiwei, please visit: http://www.art21.org/artists/ai-weiwei