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Curiosity often sparks scientific breakthroughs. For 2026 medicine laureate Peter Hegemann, it began with a question: how could a tiny green alga called Chlamydomonas react so rapidly to light? The Chlamydomonas algae is famous for its ability to swim towards light. When the alga is stirred into a petri dish, the liquid turns a faint green colour. If one side of the dish is illuminated, the green colour moves towards the light source, as the microscopic algae swim towards it. The algae sense the light with an eyespot, a dot on the cell’s surface that contains a light-capturing molecule, retinal. Hegemann discovered electrical signals in the light-sensitive eyespot that occurred just half a millisecond after illumination, far faster than the response of the human eye. He could only think of one explanation for this ultrafast response: the process must be much simpler than in a human eye. He proposed that a single protein could both detect light and act as an ion channel, an idea initially met with scepticism. After years of experiments with his colleague Georg Nagel, Hegemann's hypothesis proved to be correct. Together, they discovered proteins that functioned exactly as he had predicted: ion channels that opened in response to light. This breakthrough laid the foundation for optogenetics, a revolutionary technique that allows scientists to control individual nerve cells with light. What began as a question about a microscopic alga ultimately helped transform the field of neuroscience. Read more about the newly awarded 2026 Nobel Prize in Physiology or Medicine: bit.ly/4jNd5w7