Where do stem cells come from?
Stem cells are found in the human body in many different tissues including bone marrow, brain, blood, skeletal muscle, fat, and the skin. Stem cells are also found in placenta tissue and umbilical cord blood after birth. (http://www.stemcellresearch.org/facts/ASCpluripotency.pdf
Stem cells called embryonic stem cells develop very early in the human embryo days after fertilization. In fact, embryonic stem cells are the basic building blocks of every other tissue in the human body and during development, the embryo directs certain embryonic stem cells to become bone tissue, others to become nerve tissue, etc. until the embryonic stem cells transform into each of the other kinds of cells and tissues which make up the human body.
