This short, illustrated guide to the use of Montessori classroom materials describes how to set up a "children's house"--An environment for learning where children can be their own masters. Frames, geometrical objects, colored numerical rods, and many other items are familiar features of any Montessori classroom, and Montessori explains how to use them with preschool children to stimulate their powers of observation, recognition, judgment, and classification. She stresses that each child approaches the apparatus differently, while the role of the adult is to let the child experiment, perceive his own mistakes, and run his own risks in learning.