Cranial sutures and fontanels
Joints called cranial sutures, made of strong, fibrous tissue, hold the bones of your baby's skull together until the bones fuse, normally around age 2. Until then, the sutures intersect at the fontanels, the soft spots on your baby's head. The largest of the four fontanels is at the front of the skull (anterior); the next largest is at the back (posterior). Each side of the skull has a tiny fontanel.