Investigators have demonstrated temperature-sensitive regulation of actomyosin, a critical protein complex involved in neuronal development. By applying optically controlled heating, the team demonstrated that the protein drebrin E acts as a switch to inhibit actomyosin motility at physiological temperature, with inhibition occurring above a threshold drebrin E concentration. These findings have implications for understanding the role of temperature in embryo development and for the development of artificial nanoscale temperature sensors.