On the occasion of the 2021 Lasker Basic Medical Research Award to Karl Deisseroth, Peter Hegemann, and Dieter Oesterhelt (for “the discovery of light-sensitive microbial proteins that can activate or deactivate individual brain cells—leading to the development of optogenetics and revolutionizing neuroscience”), Deisseroth reflects on this international collaboration, his basic mechanistic and structural discoveries regarding microbial channels that transduce photons into ion current, the causal exploration of brain cell function, and the pressing mysteries of psychiatry.