Jean Piaget revolutionalized the way educators, psychologists, and researchers view children’s learning and development (Beilin, 1992). This chapter aims to give a brief history of his ideas and theory as they evolved over his lifetime and beyond, then apply many of Piaget’s concepts to the contemporary early childhood classroom. As research on all areas of child development, from brain research to social and moral research, has informed theory and practice, the strength of Piaget’s theory is how it has adapted and evolved over the last seven decades in a way that can incorporate these new findings. The first section of the chapter will introduce Piaget as a person and a theorist. An overview of key concepts of his theory will follow, with implications for practice at the end. The challenge is to capture Piaget’s theory and implications in one chapter when his work filled approximately 100 books and 600 papers, many of which have not been translated from French into English, and have multiplied exponentially by others who have written about his ideas and theories (Muller, Carpendale, & Smith, 2009). This chapter aims to present the elements of Piaget’s theory that are most informative for early childhood educators, and is by no means exhaustive in its coverage of the breadth and depth of Piagetian theory as a whole.