This chapter discusses theories of child development, theorists, curriculum models, and developmentally appropriate practices. It covers cognitive development theory from Piaget, sociocultural theory from Vygotsky, psychosocial theory from Erikson, and behavioral theory from Skinner. Curriculum models discussed include Montessori, Reggio Emilia, Bank Street, High/Scope, and cognitively oriented curriculum. The chapter emphasizes using developmentally appropriate practices, such as hands-on learning, play, and scaffolding instruction based on children's developmental levels. It also stresses the importance of positive teacher-child relationships and partnerships between families and schools.