The origami analogy fits early embryology better than late. The main organisation of the body is initially laid down by a series of foldings and invaginations of layers of cells. Once the main body plan is safely in place, later stages in development consist largely of growth, as if the embryo were being inflated, in all its parts, like a balloon. It is a very special kind of balloon, however, because different parts of the body inflate at different rates, the rates being carefully controlled. This is the important phenomenon known as allometry.
