Guanylyl cyclases (GC) are a family of transmembrane proteins that regulate physiological processes as diverse as blood pressure and our sense of smell. Neurons in the Grueneberg ganglion, a sensory organ in the mouse nose involved in detecting cold temperatures, express a subtype of GCs called GC-Gs, but scientists do not fully understand what activates these proteins. Chaoet al. now show that cool temperatures can directly activate GC-Gs, probably by driving GC-G proteins to oligomerize (group together). Mouse pups exposed to cool temperatures normally make ultrasonic cries that encourage maternal care, but pups engineered to lack GC-G proteins could not….