The need for order, exactness, self-correction and quiet reflection all are qualities that Montessori saw are needed in order for children to develop as they should. When she saw that children are particularly drawn to certain activities she then concentrated on developing materials that would extend that interest. She carefully took each of the senses and thought how best she could help the children to clarify and expand their existing experiences. By isolating specific qualities in the materials and by grading each set in ever-refined series, she was able to give the children the ability to increasingly refine each of their senses. Many of the exercises in this area are also indirect preparations for later mathematics and language work as they enable the child to order, classify, seriate and describe sensory impressions in relation to length, width, temperature, mass and colour.