Simply we can define Stem Cells as self-renewing unspecialized cells that can give rise to multiple types all of specialized cells of the body. The process by which dividing, unspecialized cells are equipped to perform specific functions for example—muscle contraction or nerve cell communication, is called differentiation, and is fundamental to the development of the mature organism.

Stem cell is a cell from the embryo fetus, or adult that has, under certain conditions, the ability to reproduce itself for long periods or, in the case of adult stem cells, throughout the life of the Organism.

Much basic understanding about embryonic stem cells has come from animal research. In the laboratory, this type of stem cell can proliferate indefinitely, a property that is not shared by adult stem cells.