Image credit: Mike Jones
This highly magnified human blastocyst (the early embryo) is about the same size as a period at the end of a printed sentence. ← (That period there is about the size...) Embryonic stem cells are created from the inner cell mass from leftover embryos at this stage after egg and sperm are mixed in a dish in a fertility clinic. Excess embryos used for research would never be used for fertility purposes, but are routinely discarded as medical waste. Photo credit: Gary Smith, PhD, University of Michigan. (text © University of Michigan Stem Cell Center.)
Magnified image of a human blastocyst. Green area is the inner cell mass, the cluster of cells along the inner wall of the blastocyst that provide the embryonic stem cells. The red cells are trophectoderm. Photo credit: Gary Smith, PhD University of Michigan. (text © University of Michigan Stem Cell Center.)
Pregnancy is usually defined in weeks, not days, from the last menstrual cycle.
Image Credit: David Rubens