Over the past 5 years, the author has visited scores of Montessori classrooms, most of them in the United States and Canada, and has observed many commonalities among them. For example, in almost every classroom, children freely chose their activities and engaged hands-on with material objects. They took care of the environment, wiping up their own spills, and dusting and sweeping. Identifiable Montessori materials, like the Pink Tower and the Metal Insets, were always present on low shelves throughout the room. There was much variety, however, in the preponderance of other materials available and in use. What might the presence and use of these alternative materials mean for the children and their education and development? In this article, the author describes the interesting history and the importance of the Montessori materials.