Karl Deisseroth, Peter Hegemann and Georg Nagel were awarded the 2026 Nobel Prize in Physiology or Medicine for developing optogenetics, a method that combines light and genes to switch neurons on or off in living brains.

Peter Hegemann and Georg Nagel discovered a protein in a single‑celled green algae that opens an ion channel when illuminated by blue light. The protein makes the algae swim toward the light source.

Karl Deisseroth, a Stanford University professor, inserted the gene that encodes this light‑sensitive protein into mouse brain cells, making those cells responsive to light – a trick he calls borrowing a solution from nature.

Researchers deliver light to the modified cells through tiny optical fibers implanted in the mouse brain. The light activates the protein and can either excite or silence the targeted neurons; newer approaches use non‑invasive light delivery but rely on the same principle.

Because the light pulses can be timed in milliseconds, scientists can control neuronal activity with the same speed the brain normally uses. This precision lets them map specific circuits that underlie behavior and disease, a shift Patrick Forcelli described as moving from a ‘road atlas’ to a ‘Google Earth’ view of the brain.

The technique is already being explored for therapies, such as restoring vision in people with inherited blindness by inserting the same light‑activated protein into retinal cells and pairing it with special light‑emitting glasses.