How did Spencer Tunick persuade more than 7,000 men, women and children to take it all off in Barcelona on June 8? "I just handed them a flyer and they came," he says. "There are always people who want to experience something new." Tunick has been finding and photographing those bold souls since 1994, when he staged his first nude "installation" in front of the United Nations. This bare-bods approach has its critics, and Tunick, 36, has been arrested for public lewdness in his native New York City (charges were dismissed). "In the U.S. people consider the naked body in public a crime," Tunick says. "But it's celebrated in other countries as something special." Not to mention a once-in-a-lifetime opportunity. Says Irene Mohedano, 34, who brought her 5-month-old Claudia to the Barcelona shoot: "This may be the only chance I get to pose for a work of art."