CRISPR Used for First Time to Study Gene Function in Human Embryos

This is a time lapse video showing the first few days of normal human embryo development. The timer at the bottom right shows how long the embryo has been developing for. From the fifth day, a stable 'blastocyst' forms - this is a ball of around 200 cells, with 180 around the perimeter that will go on to form the placenta and 20 inside that will eventually become the foetus [Dr. Kathy Niakan/Nature]