Babies generally begin to realize they are separate from their mom around 6 to 9 months of age. This awareness ties closely to the development of object permanence—the understanding that people and objects continue to exist even when out of sight—which tends to emerge around 6 to 8 months. Around this time, babies may start showing separation anxiety, becoming upset when their caregiver leaves because they understand the separation but have not yet fully grasped that their parent will return. By 12 to 18 months, toddlers increasingly understand that separation is temporary, which helps reduce their anxiety over time. This developmental milestone signals that babies are starting to see themselves as distinct individuals from their mom rather than part of an undifferentiated whole.