It is the process of gamete formation in sexually reproducing organism. Sexually reproducing organism has two types of cell somatic cell and germinal cell. Both have diploid number of chromosomes. Somatic cell forms various body organs and always multiplies by mitotic division. Germinal cell form gamete in animal body by successive mitotic and meiotic division. Process of gametogenesis is of two types: spermatogenesis and oogenesis.