At long last, researchers have zeroed in on the neurons that act as the brain's internal thermostat. Their discovery may be harnessed for therapeutic control of body temperature in conditions where it's beneficial for temperature to be reduced, such as recovery after trauma. Core body temperature, critical for survival, is normally maintained by the body within a narrow range around 37° Celsius. Despite decades of research into the internal temperature sensors in the brain responsible for this well-orchestrated effort, scientists have not been able to identify a molecular temperature sensor underlying it. Here, in samples of mouse hypothalamus - the brain center that detects and regulates internal temperature - Kun Song and colleagues identified neurons that were uniquely activated in response to warming at temperatures above the physiological set point of 37°C. These neurons expressed the ion channel TRPM2, the researchers found, and they not only detected increased temperature to prevent overheating, but - as experiments in mouse models of fever showed - limited the body's temperature rise in response to infection. The researchers' approach provides a way to remotely control core body temperature in mice, allowing for further insights of the effects of altered core body temperature on processes such as trauma recovery, energy expenditure, obesity, and longevity.