This chapter explores the multifaceted theories of cognitive development, emphasizing foundational contributions by Piaget and Vygotsky. It examines Piaget’s constructivist approach, highlighting sequential stages of development from infancy to adolescence, such as the Sensorimotor and Formal Operational Periods. These stages are tied to the interplay of neural and environmental factors, establishing a lifelong foundation for cognitive growth. The chapter also evaluates Vygotsky’s systemic perspective, where cognitive functions emerge from the interaction of biological and social systems, emphasizing the role of culture, language, and social context in development. Additional discussions include the evolution of moral reasoning, drawing distinctions between Piaget’s and Kohlberg’s frameworks, and the influence of education and parental involvement on moral and cognitive growth. The chapter underscores how early childhood environments shape intelligence, emotional regulation, and moral judgement, offering critical insights for educators and policymakers to foster optimal developmental outcomes.