What is the function of fontanels?

Fontanels are responsible for the "soft tops" on the top and back of the head. The flexibility imparted by the fontanels allows the baby's skull to deform somewhat in order to fit through the narrow birth canal during the miracle of birth. The fontanels also enable the skull to grow large as the child grows. The gaps between the infant's cranial bones gradually shrink as the fontanels are replaced by growing bone.