Embryogenesis in vitro: study of differentiation of embryonic stem cells.

Embryogenesis is the fundamental process of differentiation of all tissues from a fertilized egg. This process involves establishment of distinct stem cells that will later differentiate to all cell types. Recently, lines of embryonic stem cells have been established in culture from blastocysts. The cells are pluripotent and can differentiate in vivo to all lineages. Interestingly, differentiation of these cells can also be induced in vitro. Morphological and molecular events that are characteristic of the development of the embryo can be mimicked in vitro by growing the cells under controlled conditions. Furthermore, the process of early development can now be studied and manipulated in vitro and specific lineages of stem cells can be obtained and grown in culture.