Embryonal stem cells can be defined as stem cells derived from the undifferentiated inner mass cells of a human embryo. In other words, the cells come from the inner mass of the blastocyst. The blastocyst can be considered an early stage embryo. This means that the embryonic stem cell is grown from cells found in the embryo that are a few days old. Typically, the embryo that provides the embryonic stem cells is four or five days old. Additionally, most embryonic stem cells are obtained from embryos that develop from in vitro fertilized eggs for infertile couples. These excess fertilized eggs are donated to research with the donors' permission. Normally, embryos are not fertilized eggs in a woman's body. Embryonic stem cells have the ability to divide for long periods of time and maintain their ability to produce all cell types with a certain organism (Sidhu 7). Embryonic stem cells are distinguished by two unique properties. These are their pluripotency and their ability to replicate indefinitely (Wai Feng Lim). Embryonic stem cells are pluripotent. This implies that they [cells] are capable of differentiating into all derivatives of the three germ layers (Wai Feng Lim). These include ectoderm, mesoderm and endoderm. This means that cells may be able to develop into more than 200 cell types in the adult body, provided they are designated to do so. In addition, pluripotency allows embryonic stem cells to be distinguished from adult stem cells. On the other hand, the cells can generate all cell types in the body, while adult stem cells are multipotent. This means that they [cells] can only produce a limited number of cell types. Moreover, due to the embryo... middle of article ......c Stem cell research?" Annenberg Classroom. Np, nd Web. November 30, 2013. .Sidhu, Kuldip S. Frontiers in Pluripotent Stem Cells Research and therapeutic potential: from bench to bedside. Dubai, United Arab Emirates: Bentham Science, 2012. Internet resource Steinhoff, Gustav. From protocol to patient: Springer, 2011. Print. Turksen, Kursad. and Protocols. Totowa, NJ: Humana Press, 2002. Internet Resource. “Differentiation of Hematopoietic Cells from Embryonic and Induced Pluripotent Stem Cells.”.. 2013. .