Researchers at the Institute for Bioengineering of Catalonia (IBEC) in Spain and the University Medical Center Göttingen in Germany achieve, for the first time, in vivo light-activated auditory stimulation without the need for genetic manipulation. This new light-controlled drug, capable of triggering the neural pathways involved in hearing, can contribute to improving the spectral resolution of cochlear implants used by people with profound hearing loss or deafness.