Embryonic
Stem Cells
Are
derived from embryos. Specifically, embryonic stem cells are derived from embryos that
develop from eggs
that have been fertilized in
vitro, in an in vitro fertilization clinic, and
then donated for research purposes with informed consent of the donors. They are not derived from
eggs fertilized in a woman's body. The embryos from which human embryonic stem cells
are derived are typically four or five days old and are a hollow microscopic ball of
cells called the
blastocyst.