Exciting advances, but with immense ethical issues. Scientists can now culture and watch human embryos developing beyond the week or 10 day maximum that was possible previously. After a week or so, a blastocyte implants into the uterus and that was the point up to which observations were possible. Now there is a way to successfully culture the embryos as if they had implanted, and watch them develop. Legally a limit for research into embryos was set at 14 days, at which point the embryo is considered a living human being but there is now pressure to extend this limit.