This quick TED talk entry is courtesy of TED.com. Tour the deep dark world of the East German state security agency known as Stasi. Uniquely powerful at spying on its citizens, until the fall of the Berlin Wall in 1989 the Stasi masterminded a system of surveillance and psychological pressure that kept the country under control for decades. Hubertus Knabe studies the Stasi — and was spied on by them. He shares stunning details from the fall of a surveillance state, and shows how easy it was for neighbor to turn on neighbor.