Roderick MacKinnon is a structural biologist and neuroscientist at The Rockefeller University who received the 2003 Nobel Prize in Chemistry, shared with Peter Agre, for structural and mechanistic studies of ion channels. MacKinnon's laboratory determined the first high-resolution crystal structure of a potassium channel, providing an atomic explanation for how ion channels achieve exquisite selectivity for specific ions while conducting them at near-diffusion-limited rates. This work fundamentally advanced the field of electrophysiology and neurophysiology by providing a molecular blueprint for the channels that underlie nerve impulse propagation, cardiac rhythm, and muscle contraction. His ongoing research continues to probe the structural biology of voltage-gated ion channels, providing templates for the rational design of drugs targeting arrhythmias, pain, epilepsy, and other channelopathies. Major pharmaceutical companies use his structural data to develop selective ion channel blockers targeting neurological and cardiovascular diseases.