This is a big week for your little embryo--and in fact, at the end of this week, it will be termed a fetus, not an embryo! Although it now measures just over an inch (28-30 mm) long, about the size of an almond in its shell, and weighs just 1/30 oz (.9 g), an incredible amount of growth and development has taken place in a mere 56 days. Externally, the embryo no longer resembles a tiny sea creature: the little tail disappears, as does the webbing between the fingers and the toes. The eyes continue to move from the side to the front of the head. As they move, skin grows over them to protect the delicate cornea and quickly develops the creases that will later define the eyelids. The upper lip forms, and the folds of the ears attain their final shape.

Internally, all of the body's myriad parts--cells, tissues, organs, systems-have been differentiated. The diaphragm emerges. The heart is now functionally complete and major blood vessels assume their final plan. The lungs have divided into lobes and are filigreed with tubules, and the intestines begin to move from the umbilical cord into the body cavity.