From 4 to 6 months of age your baby will discover a little bit of the world each day. Their motor development will be obvious: They can now pick up objects, touch them, and handle them. They also establish an affective bond with the people who surround them, especially their parents, and they are able to recognise them.
At 4 months of age
They will lie on their tummy and get up using their elbows, as well as lift their head up to 90º with legs outstretched. When you put them down in a sitting position, they are able to keep their heads up. When lying on their backs, they will stretch their arms towards objects and grab them with their hands, as well as bring them to their mouths and play with them, although they are unable to retrieve them if they fall down. At this stage the lower central incisors might begin developing.
At 5 months of age
They are able to sustain most of their weight if you place them standing upright. When they hear a sound, they will turn their heads. Also, they will smile when they see their reflex in the mirror.
At 6 months of age
They get up by pushing with their wrists from a face-down position, and they begin to learn how to turn over. They can also keep upright in a sitting position and they touch their feet. They pick up the toys they are given and can pass them from hand to hand.