The formation of spermatogonia in men takes place during the embryonic period. The formation of sperm cells however is a continuous process that begins in puberty and goes on until old age and sometimes during all the remaining life of the man.

In women all oogonia are formed before birth. The oogonia turn into oocytes I that enter the first division of meiosis (meiosis I). This division however is interrupted at prophase and continues only in puberty. After the beginning of menses an egg cell is released during each period and, if fecundated, it finishes the meiotic division. The oogenesis stops after menopause (cessation of the menstrual activity) and the climacteric period of life begins.   _{Your Comment}