The state system is a fundamental component of newborn neurodevelopmental function and demonstrates the newborn's underlying neurologic and behavioral competence. The role of the state system in newborn developmental assessment reflects the newborn's ability to respond to the environment. This overview examines the importance of the state system as a significant developmental process, identifies specific variations in sleep and wakefulness, and describes behavioral patterns of state in full-term as well as high-risk newborns. Specific intervention techniques are outlined for caregivers and parents, which address consolability, adjusting the environment, handling, and interactions. This information contributes to the nurse's ability to identify and assess neurobehavioral integrity and provides appropriate behavioral individualized developmental interventions during neonatal care.