By the time you're finally feeling comfortable about breast-or bottle-feeding, or whatever combination of the two you have worked out, people will start asking you whether or not your baby has started eating solids. Odds are people will ask you sooner than they should. Until recently, moms began mixing up bowls of baby cereal when their infants were around four months old. Some started sooner in hopes that solid food would help their babies sleep longer. It didn't.