When the Nobel committee calls, scientists usually have a few minutes of stunned silence. For Karl Deisseroth, there was a second announcement to make, and the audience was waiting at home.

He won a Nobel. His 10-year-old daughter had the best review

Karl had been working late on a paper and was just starting to drift off to sleep when the call came. He had won the 2026 Nobel Prize in Physiology or Medicine, sharing it with Peter Hegemann and Georg Nagel for discoveries leading to optogenetics, a technique for switching individual nerve cells in a living brain on or off.

The clip that has people talking is the one Stanford posted on Instagram. In it, the father of five tells his two daughters, Sophie, 10, and Emma, 13, and then his son Hudson. In one frame he embraces his daughters while his wife looks on, and in another he tells Hudson, 16, the news. The line that has stuck came from Sophie. She told her dad he had won all the prizes.

The moment is so ordinary, but also so precious. The most prestigious call in science came in the middle of the night. The news reached the kids in a living room, from a dad who, per Stanford, makes his children's sandwiches every morning. Karl is hardly a newcomer to acclaim, and he is Stanford's 37th Nobel laureate. But a 10-year-old's verdict on her father's trophy shelf makes a more memorable headline than the citation does.

Stanford's own coverage tracks the same arc. There was a champagne toast on campus that Monday for the collaborators and colleagues who helped make it happen.

So what did he actually win it for?

Optogenetics sounds like science fiction: controlling brain activity with light. The idea is to give specific neurons a light switch and then flip it. Peter Hegemann found light-sensitive channel proteins in single-celled algae, and Karl Deisseroth and his Stanford colleagues delivered one of these genes into neurons using a harmless virus. The neurons then fired when light hit them. By 2007 Karl had shown it worked in live rodents and could command behaviour. Researchers can now control selected cells within large networks like the brain, with precise timing and location, using only light, so they can find out what specific cells do by switching them on and off. A technique built on pond algae and a virus now sits at the centre of modern neuroscience. The winner’s most memorable review came from his 10-year-old, in a living room, in the middle of the night.

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