Plot: Art critic Matthew Collings celebrates the birthday of one of the most successful modern art museums in the world. With contributions from director of Tate, Sir Nicholas Serota, and artists Tracey Emin, Grayson Perry, Rachel Whiteread and Olafur Eliasson, this Culture Show special asks what lies behind the extraordinary popularity of Tate Modern, with over 45 million visitors to date, and examines how this institution has changed public perceptions of art forever