The trophoblast, which is a collection of cells that invades the maternal endometrium to gain access to nutrition for the fetus, proliferates rapidly and forms a network of branching processes which cover the entire embryo and invade and destroy the maternal tissues.
As it rapidly grows, the trophoblast forms a dense network of branching processes that cover the entire embryo and invade and destroy the maternal tissues in order to obtain nutrients for the fetus.