Babies are usually ready for solid foods around 6 months old if they can hold their head up, open their mouth for food, and swallow from a spoon. Single-grain cereals mixed with breastmilk or formula are often babies' first solid food. Introduce solids gradually and check with a pediatrician to ensure the baby is developmentally ready. Dilute cereals carefully as too much or too little water can cause electrolyte issues.