Karl Deisseroth, Peter Hegemann and Georg Nagel won the prize for turning a light-sensing algal protein into a switch for nerve cells.

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• The Nobel Assembly at Karolinska Institutet announced the 2026 Nobel Prize in Physiology or Medicine on October 5, 2026.
• The prize is shared equally by Karl Deisseroth, Peter Hegemann and Georg Nagel for discoveries on light-gated ion channels and optogenetics.
• The prize amount this year is 12 million Swedish kronor.
• Hegemann and Nagel discovered a protein called channelrhodopsin in a single-celled alga that swims towards light.
• When blue light strikes the protein, a channel opens and charged ions flow into the cell, creating an electrical signal.
• The two scientists found that any cell carrying the protein became sensitive to light.
• Deisseroth introduced the channelrhodopsin gene into rat nerve cells and triggered nerve signals by shining blue light, publishing the breakthrough in 2005.
• He later made the light-controlled switch work in the brains of living mice.
• Optogenetics lets researchers switch individual nerve cells on or off in a living brain, revealing circuits behind memories, feelings and behaviours.
• Researchers have used the method to partly restore sight in people with retinitis pigmentosa, though it remains mainly a research tool.
• Deisseroth works at Stanford University, Hegemann at Humboldt University in Berlin and Nagel at the University of Würzburg.