Division of Nursing to identify risk factors for later child development. T. B. Brazelton came to consult, bringing a vibrant sense of enthusiasm for our work. His perspective on newborn behavior as evidence for how much the infant's brain was processing and responding to the environment changed our whole paradigm of infants and caregivers. We included the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) (Brazelton, 1973(Brazelton, /1984) as a primary measure in our study to evaluate how the infant's beginning capacity for sensing and reacting to her caregivers might influence later developmental outcomes.From that time until this writing, over four decades later, Dr. Brazelton and the author have both been involved in influencing our respective professions of nursing and pediatrics to focus on early development, advancing the agenda of infant mental health in our respective fields by the research and training programs we created. These training programs, the Nursing Child Assessment Satellite Training (NCAST) and the Brazelton Touchpoints Center (BTC), have continued beyond our leadership to provide scores of professionals in all disciplines with knowledge of infant behavior and development, parenting, parent-child relationships and strategies for improving healthcare for young children and their families.This chapter describes both the concepts Brazelton advanced about infant behavior and parent-infant interactions that were incorporated into a version of NCAST developed for health professions and parents called Keys to Caregiving (Sumner, 1995), as well as the author's work in infant state, state modulation and parent-child interaction.