The infant skull is composed of 7 flat membranous bones joined along their borders by fibrous joints called "sutures." These are the growth plates of the skull.
At the intersection of the sutures are larger membranes called fontanels. These are the "soft spots" of your child's head. One is located in the front and is called the anterior fontanel. It is at the intersection of the sagittal, coronal, and metopic sutures. The other, the posterior fontanel, is located in the back at the intersection of the sagittal and lambdoid sutures.
The skull grows and takes shape in response to pressure from the growing brain. The open sutures allow growth in all directions, with a slight preference for growth in the back. Brain growth determines the size and shape of the skull and is most dramatic in the first 2 years of life.