Perhaps the most recognizable Montessori materials in a Montessori school are found on the Montessori sensorial shelf area. The Pink Tower is one such Montessori sensorial material (iconic enough to appear on the logos of many Montessori schools), as is the Brown (or Broad) Stair, and the Number Rods. A common observation of nearly all parents of 3- and 4-year-olds is the tendency to “order” objects. Give a child of this age a collection of stuffed animals, and more often than not he or she will line them up from tallest to smallest. The Primary-age child possesses a developmental need, a strong need, to engage in sensory play, discriminating form and dimension. Montessori sensorial activities provide ample opportunity to satisfy. Nearly any quality that CAN be ordered is represented. Along with the aforementioned Pink Tower and Broad Stair, the Grading Tablets, Color Boxes, and Knobless Cylinders all fill this developmental need. Also present among Montessori classroom sensory materials are the Touch Boards with different surfaces, from rough to smooth, as are Baric tablets of different weights and cylinders with small button plungers that are increasingly difficult to push down (they are ordered by pressure). Montessori sensorial extensions include even thermic cylinders into which the teacher places ice or lukewarm or hot water. The young child thrives working with these Montessori sensory learning materials, because they are precisely the activities children of this age need and desire. The developmental need for the sensorial materials is present at ages 3 to 6. These Montessori sensory learning materials, comprising sensorial education in Montessori are usually limited to children under the age of seven, but they serve as an elegant indirect preparation for math, the essence of which is discrimination of size (arithmetic) and shape (geometry).