The amnion is a thin, protective membrane that surrounds the developing embryo in mammals, including humans. It forms a part of the amniotic sac, which contains amniotic fluid. This fluid cushions the embryo, providing a stable environment and allowing for movement, which is essential for proper development. The amnion plays a crucial role during pregnancy by helping to maintain temperature and protect the embryo from physical shocks. It also helps prevent dehydration by keeping the amniotic fluid contained. Overall, the amnion is vital for the healthy growth of the embryo until birth.