Biological System with Light Switch (IMAGE) Graz University of Technology Caption This is a schematic representation of the illumination of the sensor domain of a photo-receptor and the molecular propagation of the light signal to the effector (in red on the right-hand edge of the image). Credit © TU Graz/IBC Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.