English: Photo demonstration of the cremasteric muscle reflex in an adult man. The subject is a 41-year-old man whose genitals are in a flaccid, non-excited state. To demonstrate the reflex, a man pours cold and then hot water on his scrotum in the shower. With cold water, the scrotum will automatically contract to the abdominal cavity as much as possible to keep the temperature of the testicles at a higher temperature than the outside temperature. With hot water, the process is the opposite, the scrotum relaxes so that the testicles are further from the body and at the same time they automatically try to maintain their lower internal temperature. The photo does not show the maximum state of release of the scrotum, which occurs, for example, with direct sunlight on the testicles and when heat is generated on the skin, then the scrotum releases much more and the testicles hang even lower. The skin of the genitals is locally more red, it is a reaction to pouring cold and hot water. Contraction and relaxation of the scrotum is an automatically autonomous process and happens continuously throughout the day depending on the surrounding temperatures and environment.