---
title: Peter Hegemann Asked How a Tiny Alga Finds the Light, and His Curiosity Won a Nobel Prize
description: Peter Hegemann shares the 2026 Nobel Prize in Medicine after asking how a single-celled alga swims towards light. What his curiosity teaches you.
author: Dr Marina Nani (Editor-in-Chief)
date: 2026-11-08T11:32:05.298Z
updated: 2026-11-08T11:35:38.954Z
canonical: https://thequantumoflight.com/article/peter-hegemann-asked-how-a-tiny-alga-finds-the-light-and-his-curiosity-won-a-nobel-prize
image: https://cdn.nanimediahouse.com/pexels-8740297.webp
categories: Literary Culture
content_type: Feature
publication: The Quantum of Light
schema_type: Article
about:
  - type: Person
    name: Peter Hegemann
    description: Of Humboldt University of Berlin. With Georg Nagel he discovered channelrhodopsin, and shares the 2026 Nobel Prize in Physiology or Medicine.
---

Some of the greatest discoveries start with a question nobody else thinks is worth asking. For Peter Hegemann, the question was this: how does a single-celled green alga called Chlamydomonas find its way towards the light?

That question has now earned him a share of the 2026 Nobel Prize in Physiology or Medicine, with [Georg Nagel](https://thequantumoflight.com/article/georg-nagel-kept-going-until-the-signal-came-the-persistence-behind-a-nobel-prize) and [Karl Deisseroth](https://thequantumoflight.com/article/karl-deisseroth-still-sees-his-patients-the-nobel-psychiatrist-who-turned-light-into-a-switch-for-th). The Nobel Committee put it plainly in its press release: it all began with Peter Hegemann's curiosity.

## A Question Older Than Electric Light

Hegemann was born in Münster, Germany, in 1954. He earned his doctorate in 1984 at the Max Planck Institute for Biochemistry in Martinsried, where the prize-winning discoveries were made, and he is now Hertie Senior Professor of Neuroscience at Humboldt University of Berlin.

When he spoke to the Nobel Prize website after the announcement, he traced his question back much further than his own career. The first publication on how Chlamydomonas senses light appeared in 1866, written by a Russian scientist who studied the alga in water from the river Neva in St Petersburg. That scientist worked without electricity, and Hegemann still admires how carefully the experiments were described.

More than a century later, in the early 2000s, Hegemann and Nagel found the answer: a protein on the surface of the alga, which they named channelrhodopsin. When blue light falls on it, a channel opens and charged particles flow into the cell, creating an electrical impulse. Whatever kind of cell they put the protein into, that cell became sensitive to light.

## From Pond Scum to the Human Brain

When the discovery was first published, Hegemann remembers, a leading journal described it as an ion channel from pond scum. The community of scientists who study Chlamydomonas was not amused.

The pond scum had the last laugh. Karl Deisseroth placed the protein in nerve cells, and optogenetics was born: a way of switching specific brain cells on and off with light. Today it is used in laboratories around the world to map the circuits behind memory, emotion and behaviour, and in attempts to restore sight.

Hegemann almost missed the news of his prize. An email from a stranger asked him to call back about something important. He nearly ignored it, until he noticed the Swedish dialling code, which he recognised from his years of sailing. The caller was the chair of the Nobel Committee, shortly before 11am.

## Work on Something New

Journalists keep asking Hegemann what the next generation should do to improve optogenetics. His answer surprises them. They should not try to improve it, he says. They should work on something new, and look at the many interesting creatures still to be studied.

That advice reaches far beyond science.

**Follow the question that will not leave you alone.** Hegemann did not set out to transform neuroscience. He set out to understand how an alga finds the light. Curiosity is not a distraction from your purpose. Very often, it is your purpose trying to get your attention.

**Respect the small things.** A journal called his organism pond scum. Your own small interests, the hobby you are shy about or the subject nobody at work cares about, may hold more value than you think.

**Do not polish someone else's success.** It is tempting to improve what already works. [The greater leaps come from people who look where nobody is looking](https://thequantumoflight.com/article/henri-kagan-questioned-what-every-chemist-assumed-and-won-the-nobel-prize-at-95). Before the year ends, write down one subject you would study if nobody were judging you, and spend an hour on it.

**Share the credit with your friends.** Hegemann's first thought, he said, was the pleasure of sharing the prize with two close collaborators he counts as friends. Great work is rarely done alone.

## The Light You Swim Towards

A single-celled alga has no brain, yet it finds the light and swims towards it. You have the most complex brain in the known universe, and in these darker November weeks it is worth asking the same question Hegemann asked: what is your light, and are you swimming towards it?