Stage 3 Mix-Ins is a natural progression for when your baby completes Stage 2 Mix-Ins or is consistently eating solid foods. To note, you can't add Stage 3 Mix-Ins to a bottle. Stage 3 Mix-Ins can only be added to your baby's food such as purees. If your baby is not consistently eating solids, Stages 1 and 2 offer a great way to feed your baby the most important allergens through a bottle of breast milk or formula. You can also use Stage 2 Mix-Ins while transitioning to solids.