[Source: Science Daily]
The human skull is made up from several bones that are connected by tough fibrous tissue called sutures. These sutures give the skull some flexibility, allowing the head to pass through the birth canal.
Where several sutures meet, they create a fontanel. Fontanels make the skull flexible enough for the brain to grow. When a child is born, it will have several fontanels on the skull, but the ones on the back (posterior) and top (anterior) of its head are the most well-known.
For many babies, only the larger anterior fontanel is open after birth. People refer to this fontanel as the soft spot.