The topic of stem cells can become a very controversial topic in the world of scientific research. Stem cells act as an internal repair system to restore other cells while the person or animal is still alive. In this way, many deadly and incurable diseases such as leukemia and Parkinson's disease could be treated and cured. The origin of stem cells is what sparks great controversy across the nation and the world. Until recently, scientists worked primarily with two types of stem cells: embryonic stem cells and non-embryonic or “adult” stem cells. Embryonic stem cells are derived from embryos, as the name suggests, so many believe this is morally and ethically wrong. Stem cells have the ability to develop into many different cell types in the body throughout life and growth. Examples include the bone marrow, heart, and pancreas. Stem cells have two important characteristics. First, they are unspecialized cells capable of renewing themselves through cell division. Unspecialized stem cells are cells that have no special function. Second, they can be generated to become tissue- or organ-specific cells with special functions. Stem cells divide to repair and replace worn or damaged tissue, sometimes regularly or under special conditions depending on the tissue type (Stem Cell Basics, 2009). Stem cells are very important for living organisms to stay healthy and survive, and for many other reasons. In a blastocyst, which is a three- to five-day-old embryo, the internal cells give rise to the entire body of the organism. All stem cells have three unique and general properties: they are capable of immersing and renewing themselves for long periods, they are not specialized and can give rise to species... middle of paper... therapeutic purpose - a hope for a new horizon in biotechnology medical. Journal of Experimental Therapy and Oncology, 8(3), 223-233. Retrieved from EBSCOhost.Stem Cell Basics [Stem Cell Information]. (2009). NIH stem cell information home page. Retrieved October 6, 2011, from http://stemcells.nih.gov/info/basiTop 10 Facts About Stem Cell Treatment | A closer look. (n.d.). A closer look. Retrieved October 27, 2011, from http://www.closerlookatstemcells.org/Top_10_Stem_Cell_Treatment_Facts.htmYoon-Young, J., Zhaohui, Y., & Linzhao, C. (2011). Molecular imaging and stem cell research. Molecular Imaging, 10(2), 111-112. doi:10.2310/7290.2010.00046Zacharias, D. G., Nelson, T. J., Mueller, P. S., & Hook, C. (2001). The science and ethics of induced pluripotency: what will become of embryonic stem cells?. Mayo Clinic Proceedings, 86(7), 634-640. doi:10.4065/mcp.2011.0054