A brain computer interface (BCI) is any technology that allows you to connect your 3 pounds of wetware to a computer. But instead of implanting electrodes via neurosurgery, might the next revolution in BCIs come from something very small, like nanoparticles? Would this allow us to spy on millions (or billions) of neurons talking at once -- and could we do so without opening the skull? Will this allow BCI tech to become as common as smartphones? Join Eagleman as he talks with the company Subsense about why the next brain-computer interface might come from thinking small.