The term differentiation means that
original cells, whether or not postmitotic,
can require other qualities than the
original cell.
Having reached the 16-cell stage, some of
the blastomeres end up in the centre of the
morula These are fully surrounded by more
peripheral cells.
The peripheral cells, with a differentiated
outer cell membrane compared to the central
cells, differentiate into trophoblast
cells.
The central cells remain omnipotent for a
while, they can differentiate into either
trophoblast or embryoblast cells. The
embryoblast cells develop into the actual
embryo.