Stem cells is a group of cells which are undifferentiated and hence they have the ability to further differentiate into some or the other kind of specialized cells. Two sources of stem cells are there in an individual i.e; Embryonic stem cells and Adult stem cells. Embryonic stem cells are derived from a four- or five-day-old human embryo that is in the blastocyst phase of development. Adult or somatic stem cells exist throughout the body after embryonic development and are found inside of different types of tissue.an undifferentiated cell of a multicellular organism which is capable of giving rise to indefinitely more cells of the same type, and from which certain other kinds of cell arise by differentiation. They are passed from mother to the foetus.