Dr Montessori identified what she called the four planes of development.
The first of these is the period from 0-3. The importance of this phase is the building of the foundation on which everything to come must stand. Just as the physical embryo develops hidden within the mother during pregnancy, the “psychic embryo” develops all the human characteristics of strength, intelligence, language, and independent human movement (walking) in the first three years. Through the acquisition of these characteristics the child adapts to his environment.