Step 1: Nipple Top 3 months and up - Designed for newborn Ideal design of nipple contour fits baby's mouth, creating a sensation similar to suckling at a mother's breast - Step 2: Spout Top 5 months and up - Designed for weaning Flexible spout allows babies to adjust the flow of liquid, allowing those who continue drinking in a breast-suckling manner to make a smoother transition from breast to cup - Step 3: Straw Top 8 months and up - Designed for teething Perfect softness of straw fits baby's sensitive mouth, helping baby make the transition of drinking liquids on his own