A Tattoo Artist tattooes a man during the International Tattoo Convention on March 22, 2013 in Frankfurt am Main, Germany. The Frankfurt tattoo convention is considered the world's biggest fair for the art of tattooing. More than 700 artists from all over the world will make more than 3,000 tattoos at the three-day show. The Hessian state laboratory has found carcinogens in some tattoo inks produced in China, causing warnings to be issued Europe-wide.