Maria Montessori used the phrase “sensitive periods” to describe the child’s development within each plane. A sensitive period refers to a time when a child is especially in tune, especially ready, especially compelled to work on activities that satisfy the need of that developmental stage. It is temporary and, if missed, cannot be reacquired. A commonly understood example we can use to illustrate this concept is the acquisition of language. A child in the first plane of development is “wired” to acquire language in much the same way that a plant is “wired” to send out roots or begin to form a bloom. A child who is not provided an environment that supports this sensitive period for speech and communication will have a much more difficult task in attempting to acquire these skills at a later age. In the same way, Montessori identified 11 separate sensitive periods. When we speak of children being “inner directed,” it is to these sensitive periods, a term borrowed from botany, to which we refer. Starting in the first plane of development, they include a sensitivity to movement, music, grace, courtesy, and order. During the second plane of development, from 6 to 12 years of age, the child develops a sensitive period for the use of imagination, for acquisition of culture, and for a strong sense of the social realm. There also exists a strong motivation for the learning of facts and nomenclature, as well as a sensitive period for the study of morality, right and wrong, and justice. A child in the third plane of development, from 12 to 18 years of age, is in a sensitive period for tremendous abstract thought, for delving into great detail on specific topics, for thinking in global terms, and for taking on adult roles.