The document discusses Montessori's theory of sensitive periods in child development. It explains that sensitive periods are times of heightened interest in specific skills like language, movement, and mathematics. During these periods, children can make significant progress but the windows of opportunity are limited. The document outlines 11 sensitive periods identified by Montessori from birth to age 6, including those for order, movement, small objects, and various academic skills. It concludes that allowing children freedom within a prepared learning environment supports optimal development during these critical phases.