'''Embryonic stem cells''' are taken from the inner part of a young embryo, also known as a [[blastocyst]]. An embryo reaches the blastocyst stage about 4-5 days after [[fertilization]]. At that point they contain about 50-150 cells. | '''Embryonic stem cells''' are taken from the inner part of a young embryo, also known as a [[blastocyst]]. An embryo reaches the blastocyst stage about 4-5 days after [[fertilization]]. At that point they contain about 50-150 cells. |