One of the enduring tasks of neuroscientists has been to uncover the secrets of the nerve impulse—the astonishingly efficient electrical signaling mechanism that enables the brain to carry out its functions and which is responsible for all our thoughts, feelings, sensations and actions. Beginning with the experiments of Galvani on the frog’s leg more than 200 years ago, the task has called for great ingenuity and determination, and has finally been completed. The results have not only been of great interest in themselves but have shed new light on a host of clinical disorders.