جان بياجيه was a Swiss psychologist known for his work in developmental psychology. He is best known for his theory of cognitive development, which outlines how children progress through four stages: sensorimotor, preoperational, concrete operational, and formal operational. His research emphasized the importance of play and exploration in learning. His ideas have significantly influenced education and psychology, highlighting how children think differently than adults. Piaget's theories encourage educators to create learning environments that foster curiosity and critical thinking, allowing children to construct their own understanding of the world around them.