The sensorimotor stage is the first of the five stages in Jean Piaget's theory of cognitive development. It occurs from birth to about 2 years old. During this time, infants learn about the world through their senses and actions. They explore their environment by touching, looking, and moving, which helps them understand how things work. In this stage, babies develop important skills like object permanence, which is the understanding that objects continue to exist even when they can't be seen. For example, if a toy is hidden under a blanket, a child in the sensorimotor stage will eventually learn to look for it, showing their growing cognitive abilities.