According to Wikipedia, Stem cells are cells common to all multi-cellular organisms that hold the ability to renew themselves through cell division and can differentiate into a wide range of specialised cell types.

The three categories of stem cells are considered to be:

Fisrt, embryonic stem cells, that are derived from blastocysts, then adult stem cells, which are found in adult tissues and finally, cord blood stem cells, which are found in the umbilical cord blood. In a developing embryo, stem cells are able to differentiate into all of the specialised embryonic tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing specialised cells. Research in the human stem cell field is growing year after year as scientists find more and more use for stem cells.

Stem cells, which are the precursor cells that give rise to the 210 different kinds of tissue in the human body, are believed to have the potential to treat diseases such as Alzheimer's, Parkinson's, diabetes, and cancer.

Human embryonic stem cell research may indeed have the potential to benefit many people who suffer from serious debilitating conditions. Because embryonic stem cells can develop into many different types of tissues, researchers hope these cells can be coaxed into replacing tissues whose function has been lost or compromised as a result of injury or disease.

On the other hand, the use of embryonic stem cells in research is raising a big debate. As scientists start speaking about cloning to produce human embryonic stem cells for use of medical therapies, some people seem to have a moral issue with the practice of cloning. The stem cell/cloning controversy raises, once again, the fundamental issue of personhood and the ensuing considerations of how human persons should be treated.

It would be interesting to see how people’s way of thinking will evolve in the future and to see whether or not, stem cells will be used to treat some diseases.