Scientists have discovered a group of extraordinary microbial molecules found in exclusively cold environments, such as glaciers. The molecules, which they called ‘cryorhodopsins’, allow microbes to absorb energy from sunlight, similarly to chlorophyll, and can be engineered to act as a light-operated power switch for electrical activity in neurons. Some of them are blue – a rare light absorption property that can have wide applications in many scientific fields. Cryorhodopsins are the first observed prototypical switches that turn electrical signalling in cells both on and off depending on the colour of light they receive – a remarkable ability that offers new possibilities for science and medicine. The study was led by a scientist at the European Molecular Biology Laboratory (EMBL) in Hamburg and involved scientists from Germany’s University Medical Center Göttingen and Goethe University Frankfurt, as well as from the University of Groningen in the Netherlands, and others.