The so-called “tummy time” is a recommended activity that you do with your child only after she has developed the ability to control her head. For most parents, this simply means putting their baby on her stomach and allowing her play in that position to facilitate the development of the baby’s ability to lift her head and hold her body in extension. This control eventually allows the baby to develop the ability to roll over, and all of that control is what will eventually allow the baby to sit up.