In an astonishing talk and tech demo, neurotechnologist Conor Russomanno shares his work building brain-computer interfaces that could enable us to control the external world with our minds. He discusses the quickly advancing possibilities of this field -- including the promise of a "closed-loop system" that could both record and stimulate brain activity -- and invites neurohacker Christian Bayerlein onto the TED stage to fly a mind-controlled drone by using a biosensing headset.