After breast-milk or formula, they're your baby's next stop on the road to healthy eating.
For the first few months of life, a baby's digestive system isn't ready for solids.
But once babies reach four to six months, they are physically, and usually psychologically, ready to try new tastes and textures.
By this time, babies are watching their parents eat and acting interested.
If you wait to introduce solid foods until the baby is a year old, it will be very difficult for the baby to make a quick switch - old habits are hard to break, even for babies.
Thin consistency at first
The best solid food to introduce first is rice cereal. Not only are baby rice cereals iron-fortified - babies this age need extra iron for rapid growth - they are also unlikely to cause allergic reactions.
For the first few feedings, mix a couple of spoons of cereal with breast-milk or formula, making it the consistency of thin gravy. As time goes on, you can increase the thickness and quantity.
Once your baby can handle cereal, the next step is usually strained or pureed fruits and vegetables, either from a jar or prepared at home.
Start with one or two spoonsful and gradually work up to half-a-cup per day, depending on baby's appetite.
Introduce solid foods one at a time. Offer a new food every three to five days.
This will give the baby's system time to adjust and also give you an opportunity to watch for any allergic reactions such as a rash, diarrhea, vomiting or stuffy nose.
The choice is yours
If you notice any of these symptoms, stop feeding the suspected food and tell your baby's doctor about it at your next visit.
Some baby care experts advise giving fruits before vegetables because babies are eager to take them; others say vegetables should come first because once babies get used to the sweetness of fruit, they tend to refuse less sweet foods.
Physically and nutritionally, it doesn't really matter, so the choice is yours.
Other foods and drinks you can introduce by six months are 100 percent fortified fruit juices (except orange juice) and plain yogurt.
Don't be surprised if your baby balks at the first few feedings of solid food - it's a brand new experience. With time, your baby will become a pro.
Make feedings a pleasant experience: go slowly and never force a baby to eat more than he or she wants.
For your baby, this is the start of a lifetime relationship with food. You want it to be a healthy, happy beginning.