2 min readOct 6, 2026 06:15 AM IST First published on: Oct 6, 2026 at 06:15 AM ISTIn the beginning was a single cell, instinctively moving towards light so that the business of living may continue. For German photobiologist Peter Hegemann, studying the microscopic alga known as Chlamydomonas in the 1990s, the question was straightforward: How did this simple organism respond to light in one-twentieth of the time that it took the human eye to see? The simplicity of the alga’s biology, it turned out, was the key needed to unlock the complexities of the human brain, from how different organs are controlled to where feelings, memory, even consciousness itself, reside.In awarding the 2026 Nobel Prize in Physiology or Medicine to Hegemann, American neuroscientist Karl Deisseroth and German biophysicist Georg Nagel, the Nobel Assembly has recognised what is effectively a new era in neuroscience. Hegemann, along with Nagel, discovered channelrhodopsin, a protein that enables Chlamydomonas to react to light in half a millisecond — compared to the 10 milliseconds that it takes the human eye to process information. Deisseroth then used it to develop a “light switch” that can control nerve cells, thus inaugurating the field of optogenetics.AdvertisementThe pinprick of illumination that was made by Hegemann’s curiosity has since expanded to shed light on neural pathways that could once only be guessed at. Researchers have been able to identify the precise circuits that control functions and behaviours, from why some people develop a greater preference for sugar to how the rhythms of the heart can affect emotions and how the brain stores information about fear, anxiety and depression. It offers hope for a greater understanding of psychiatric and neurological disorders — areas of darkness that could soon become less intimidating.