Time Out says
The Darwin Centre, opened in September 2009, is an enormous 65-metre-long, eight-storey-high cocoon – the largest sprayed concrete, curved structure in Europe – that houses the Natural History Museum's insect and plant collections. Travelling up to the seventh floor in scenic lifts you'll get amazing views of Alfred Waterhouse's original Victorian terracotta building, itself one of the most beautiful in the world. The Darwin Centre Cocoon contains state-of-the art laboratories where scientists extract, process, sequence and analyse the DNA of plants and insects. As in the neighbouring Spirit Collection for zoology, the cocoon strives to remind visitors that the museum is a living, breathing research scientific establishment, not just a collection of dead stuff in cases. Not that the dead stuff in cases isn't interesting or important in itself and there are hundreds of real plants and insects from huge tarantulas to metre-high poisonous plants. A highlight is a wall of 326 specimens that spreads over two floors, from a half-metre crayfish to a tiny wingless termite. Adm is free but booking is required (self-guided visits last around 45 minutes). The Attenborough Studio is a state-of-the-art communication centre and home to a programme of informal daily discussions at which you can discover more about the work of some of the 350 museum scientists and world-class experts using cutting edge technology, real specimens or even live animals. The museum is open until 10.30pm on the last Friday of every month (excluding December) and it's free to visit the Darwin Centre and Cocoon experience (which close at 10pm) during After Hours (book your tickets online in advance, or you can pick up free tickets on arrival at the Museum).