In Piaget's theory, grasping the notion of object permanence marks the transition from the "sensorimotor stage" to the "preoperational stage".
The sensorimotor period alludes to the most early stage which is from birth to 2 years, in Jean Piaget's theory of cognitive development. This stage is portrayed as the time of a child's life when learning happens through a child's sensory and motor interact with the physical surrounding.