4 month old babies really start to be more aware of the world. They start cooing and laughing at you. They sometimes scream when they are happy. They start putting everything in their mouth and they can see you and track you as you walk across the room. Some babies can start rolling over from their backs to their bellies and the other way around. We start to recommend introducing cereals between 4-6 months of age when your baby is ready. Their necks are a little bit more stable. You would not see a lot of tongue thrusting at this point. Parents it is time to start child-proofing your house at this age while you still have time before they become more mobile.