Arnold Gesell was an American psychologist and pediatrician known for his work in child development. Born in 1880, he developed the concept of developmental milestones, which are key stages that children typically reach as they grow. His research focused on how children develop physically, socially, and emotionally, providing valuable insights for parents and educators. Gesell founded the Gesell Institute of Human Development in 1940, which aimed to promote understanding of child growth and behavior. He also created the Gesell Developmental Schedules, a tool used to assess children's development and identify any potential delays. His contributions have had a lasting impact on the fields of psychology and education.