Tummy time is when you put your baby on his or her stomach while awake and under supervision. This helps the baby develop a strong neck and shoulder muscles. It can also promote motor skills. Spending time on its belly can also prevent the baby from developing flat spots on the back of the head (plagiocephaly). If the baby’s head is left in the same position for an extended period of time, the bone plate of the skull will move to create a flat tip.