Cells in an embryo begin deciding their future only two days after conception, when the embryo is made up of just four seemingly identical cells.
By the time the embryo implants in the uterus lining, it has become a blastocyst, made up of hundreds of cells, some of which will become the placenta, and some the fetus. We know that around this stage – days eight to 16 after fertilisation – the cells have taken on a range of varying roles, but it has been unclear when our cells first decide what it is that they should become.
Read more in New Scientist | Published in Cell: DOI: 10.1016/j.cell.2016.01.047