Embryonic stem (ES) cells was isolated from blastocysts and grown as a cell line in culture.ES cells are pluripotent cells, which can comprise all the tissues of chimeras in vivo and differentiate into many cell types in vitro.It has been shown that it may be possible to generate germ cells from ES cells in culture.The germ cell lineage is the source of totipotency, ensuring the creation of new organisms.In mice, primordial germ cells (PGCs) emerge from the proximal epiblast cells.Genetic studies have demonstrated that signals from BMP and SCF play essential roles in the process of PGC specification.In male mice, PGCs initiate migration, passing through a developing hindgut, colonizing the embryonic gonads and maintaining the production of sperm by mitosis and meiosis.