One of Maria Montessori's most important observations was that as children grow from birth to adulthood they move through a series of developmental phases, which she termed planes of development. Dr. Montessori likened the stark differences between developmental stages to the metamorphosis from larva to butterfly – where each phase is so different that the organism appears to have reinvented itself.
While each plane is markedly different from the others, all have specific and natural developmental goals. Each plane is also marked by sensitive periods where children seek specific stimuli with such intensity that they can easily master a skill. An example is a young child’s ability to acquire multiple languages with relative ease. Success in each plane is dependent upon how well developmental needs were met in the previous plane.