Musk is a name that originally designated a strong-smelling brownish substance secreted by the male of the musk deer of the genus Moschus. Each of the adult male representatives of this animal species has a musk gland that lies in a sac positioned between the genitals and the umbilicus, and secretes powerful pheromones used to attract mates. It has been rumored since ancient times that wonderful musk odor works as an excellent aphrodisiac, and modern science has offered an explanation for this. Even though the debate on the existence of sex pheromones continues, there are scientists who believe that the smell of musk closely resembles the smell of testosterone, which may act as a pheromone in humans.