摘要One of the wel -defined sexual y dimorphic structures in the brain is the sexual y dimorphic nucleus, a cluster of cells located in the preoptic area of the hypothalamus. The rodent sexual y dimorphic nucleus of the preoptic area can be delineated histological y using conventional Nissl staining or immunohistochemical y using calbindin D28K immunoreactivity. There is increasing use of the bindin D28K-delineated neural cluster to define the sexual y dimorphic nucleus of the preoptic area in rodents. Several mechanisms are proposed to underlie the processes that contribute to the sexual dimorphism (size difference) of the sexual y dimorphic nucleus of the preoptic area. Recent evidence indicates that stem cellactivity, including proliferation and migration presumably from the 3rd ventricle stem cellniche, may play a critical role in the postnatal development of the sexual y dimorphic nucleus of the preoptic area and its distinguishing sexual y dimorphic feature: a signifi-cantly larger volume in males. Sex hormones and estrogen-like compounds can affect the size of the sexual y dimorphic nucleus of the preoptic area. Despite considerable research, it remains un-clear whether estrogen-like compounds and/or sex hormones increase size of the sexual y dimor-phic nucleus of the preoptic area via an increase in stem cellactivity originating from the 3rd ventricle stem cellniche.