What Are Embryonic Stem Cells? What Are Adult Stem Cells?

Well you may already know that stem cells are those cells of a living organism that can subdivide virtually endlessly into other cells (like nerve, muscle, etc.,) to repair or regenerate tissue.  Embryonic stem cells derive from embryos created during in vitro fertilization process--ones which would not otherwise be implanted or become a pregnancy.  (They are donated to research instead of being discarded).  Embryonic stem cells are never derived from an egg that is fertilized in a woman's body/has been implanted or a pregnancy.)  At any rate, these embryonic stem cells are capable of becoming any kind of cell, whereas adult stem cells are more limited -- and some may only be capable of becoming same kind of cell of the tissues in which they derive. There are only a very small number of stem cells in adult tissue.  Scientists still do not know if adult stem cells are "leftover" from the embryonic period or if they occur/develop or appear in some other way. Also, great numbers of embryonic stem cells can be grown in cultures in the lab, but it is more challenging to grow large cultures of adult stem cells.  Both kinds of stem cells (embryonic and adult) are being researched for their use in cell based therapy for treatment of disease.

Adult stem cells hold far more promise for therapeutic use - because they are your own cells, so they have your own DNA.

The moral argument against using embryonic cells, is that you are creating a living being that you are then using as if it were a product.