The second idea, that cells in the early embryo are unspecialised, has been
challenged by recent findings at the University of Cambridge, UK1. Researchers
separately dyed the cells of a mouse embryo at the two-cell stage, one red, the other
blue, and then allowed the embryo to continue developing. They then followed the
differently coloured multiplying cells to the blastocyst stage, noting that one of the
cells gave rise to the embryo body and the other to the tissues that support the
developing embryo. This indicates that even at this most early of stages the two cells
are different from one another and are committed to a particular pathway.