Have you ever wondered how Daleks climb stairs? How Cybermen make little Cybermen? Or where the toilets are on the Tardis? Doctor Who arrived on TV screens in 1963. Since then, across light years and through millennia, the journeys of the Time Lord have shown us alien worlds, strange life forms, futuristic technology and mind-bending cosmic phenomena. Viewers cowered terrified of Daleks, were amazed with the wonders of time travel, and travelled through black holes into other universes and new dimensions. The breadth and imagination of the Doctor's adventures have made the show one of science fiction's truly monumental success stories. BBC Focus editor Paul Parsons explains the scientific reality behind the fiction. Discover: why time travel isn't ruled out by the laws of physics the real K-9 ? the robot assistant for space travellers built by NASA how genetic engineering is being used to breed Dalek-like designer life forms why before long we could all be regenerating like a Time Lord the medical truth about the Doctor's two hearts, and the real creature with five of them.