Each tool in the program is focused only on developing one sense, such as, for example hearing or vision. Sensory material is not and must never substitute objects of life, to serve as a key to differentiation. With sensory material children work from the moment they are able to classify various items. Children learn not only to recognize the different senses and their capacity, but also to use Montessori teaching aids to perceive and understand the different characteristics of things. Therefore they acquire skills that help them to understand the world around them.