The 2026 Nobel Prize in Physiology or Medicine just went to Karl Deisseroth, Peter Hegemann and Georg Nagel. Here's what you need to know. The Nobel Assembly at Karolinska announced the prize today "for their discoveries concerning light-gated ion channels and optogenetics." Deisseroth is from the U.S. Hegemann and Nagel are from Germany. The committee calls optogenetics a method that shows how nerve cells shape memories, feelings and behaviours. The story starts with an alga. Hegemann wondered how Chlamydomonas, a single-celled alga, swims towards a light source. In the early 2000s, he and Nagel discovered a protein called channelrhodopsin in it. It is a light-gated ion channel. Then Deisseroth turned it into a tool. He put the gene for channelrhodopsin into nerve cells from rats. When he lit the cells with blue light, he could switch them on. Channelrhodopsin became a light-controlled switch for nerve cells. Why it matters. Understanding how the brain forms memories, feelings and behaviours has long been a dream for researchers. Using optogenetics, they can now reveal the neural circuits behind specific memories, feelings and behaviours relevant to neurological and psychiatric conditions. The Nobel committee says the laureates laid the foundation of a new era in neuroscience. Key numbers: - 3 laureates: Deisseroth (U.S.), Hegemann (Germany), Nagel (Germany) - Announced at 11:30 CEST by the Nobel Assembly - Channelrhodopsin found in the early 2000s - Blue light used to activate rat nerve cells Optogenetics lets scientists turn nerve cells on and off with light-sensitive proteins from algae, and it is now a core tool in brain research.