Thomas Perlmann, secretary general of the Nobel Assembly at the Karolinska Institutet, explained that optogenetics “makes it possible to switch on, or off, the activity of individual nerve cells in a living brain” using light‑gated ion channels.

In the early 1990s, Peter Hegemann hypothesised that a single protein in the green alga Chlamydomonas could capture light and act as an ion channel. Georg Nagel tested this idea by inserting Chlamydomonas genes into frog eggs and discovered channelrhodopsin‑2, an ion channel that opens when exposed to light.

The team showed in 2003 that the protein could be introduced into human and hamster cells, where light triggered electrical impulses. Two years later, Karl Deisseroth demonstrated the same principle in rat nerve cells and, in 2006, coined the term optogenetics for the technique.

Today the method is used in laboratories worldwide to map brain circuits. Researchers are also testing it in clinical trials: by inserting a light‑sensitive protein into the retina, they aim to restore vision for patients with retinitis pigmentosa, and they hope it will make cochlear implants stimulate the auditory nerve more precisely. “The patients lose their photoreceptors, but healthy cells remain,” said Per Svenningsson, professor of neurology at the Karolinska Institute.