In general, cell can be defined as an autonomous self replicating unit that may constitute an organism (in the case of unicellular organisms) or be a sub unit of multicellular organisms in which individual cells may be more or less specialized differentiated  for particular functions.

Stem cells are primal undifferentiated cells which retain the ability to differentiate into another cell types under correct inducing conditions. This ability allows them to act as a repair system for the body; replenishing other cells as long as the organism is alive The profound character of a stem cell is its extensive cell renewal capacity and its multilineage differential potential. Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cells that renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas. All stem cells—regardless of their source—have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types.

Stem cells are unspecialized but have an ability to give rise to specialized cells. When unspecialized cells give rise to specialized cells, the process is called differentiation. One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells. Stem cells are also capable of dividing and renewing themselves for long periods. Unlike muscle cells, blood cells, or nerve cells—which do not normally replicate themselves—stem cells may replicate many times. When cells replicate themselves many times over it is called proliferation.

Basically, stem cells can be of two types, namely, embryonic stem cells and adult stem cells. Embryonic stem cells are the primitive (undifferentiated) cells from the embryo that have the potential to become a wide variety of specialized cell types. Specifically, embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro- in and in-vitro fertilization clinic- and then donated for research purposes with informed consent of the donors. Where as, adult stem cells are the undifferentiated cell found among differentiated cells in a tissue or organ, can renew itself, and can differentiate to yield the major specialized cell types of the tissue or organ.

Scientist believe that these cells can be directed in the laboratory to differentiate in any cell or tissue to treat many diseases like Parkinson’s disease, Alzheimer’s disease, leukemia, rheumatoid arthritis, cancer etc. Researches on stem cells also promise to improve our understanding of complexities and the disease process.  It is expected to provide unlimited supply of tissues and organs for transplantation which are in great short supply. Stem cells offer the opportunity of transplanting a live source for self-regeneration. Bone marrow transplantation (BMT) is a well known clinical application of stem cell transplantation.

With the advancement of technology and research in these stem cells transplantation, the day will come, where we can buy the organ of our interest from medical shop and there won’t be shortage of any organ or tissue for transplantation.