Piaget is best known for his work in which area of development?

Piaget is best known for his work in cognitive development, which focuses on how children acquire, construct, and use their understanding of the world. His theory emphasizes the stages of cognitive development, outlining how a child's thought processes evolve throughout infancy and childhood.

Piaget proposed that cognitive development occurs in distinct stages: sensorimotor, preoperational, concrete operational, and formal operational. Each of these stages reflects a different way in which children think and understand their environment. His observations and experiments demonstrated that children's cognitive abilities are not simply smaller versions of adult thinking; rather, they develop through a series of qualitative changes.

This foundational work has had a lasting impact on education and developmental psychology, emphasizing the importance of active learning and the concept that children construct knowledge through interaction with their environment. Thus, Piaget's legacy primarily resides in the field of cognitive development.