Will Gompertz celebrates Museums at Night, a three day festival of museums and galleries from St Ives to Orkney that throw open their doors till late, showcase their collections and party! At the National Museum of Scotland Will hears a pop up opera, visits a silent disco and enjoys a gramophone DJ set. Discussing the exciting renaissance of our museums and galleries, historian and presenter Bettany Hughes, head of London's South Bank Centre Jude Kelly, Google's Amit Sood and actor Mat Fraser also enjoy live music, aerial performances and the museum's amazing collection, all under the watchful gaze of Dolly the Sheep, the world's first cloned mammal. There are also short films showcasing Museums at Night events across the country. We go to Nottingham where renowned photographer Rankin shoots, prints and shows an exhibition in just one day. Andrew Graham-Dixon goes behind the scenes at the National Gallery after dark to get a sneak preview of a hidden masterpiece and we take a safari around the Yorkshire Sculpture Park.