Dr. Maria Montessori developed what became known as "The Montessori Method" as an outgrowth of her post-graduate research into the intellectual development of children with intellectual disabilities. Building on the work of French physicians Jean Itard and Edouard Seguin, she attempted to build an environment for the scientific study of children with various sorts of physical and intellectual disabilities. Following successes in the treatment of these children, she began to research the application of her techniques to the education of children of average intelligence.
By 1906, Dr. Montessori was well-known and she was asked to run a day-care center in the run-down San Lorenzo district of Rome. She used the opportunity to observe the children's interactions with materials she developed. She refined the materials and developed new materials with which the children could work. This material-centered approach, in which the teacher primarily observes while the children select materials designed to impart specific concepts or skills, is a hallmark of Montessori education.
Montessori's initial work was primarily with preschool-aged children. After observing developmental changes occurring in children who are just beginning elementary school, she and her son Mario began a new course of research into adapting her approach to elementary-aged children. Toward the end of her life, in her book From Childhood to Adolescence, Montessori sketched out a view of how her teaching methodology might be applied to the secondary and university levels.