Official definition of human embryonic stem cells widened in US
February 24, 2010
The official definition of human embryonic stem (HES) cells in US National Institutes of Health (NIH) guidelines is to be broadened from those ‘derived from the inner cell mass of blastocyst stage human embryo’ (ie. from embryos that have reached the blastocyst stage at four or five days old, 70-100 cells), to include also those derived from earlier stage embryos. (PHG Foundation)
