The second Montessori Mobile, The Octahedron Mobile, is introduced right around 7 weeks when the newborn is able to percieve the difference in contrast between the bright primary colors. The three-dimensional octahedrons of differing sizes are made from shiny, metallic paper and hung at different lengths with thread. The movement and light created when the objects swing in the natural air current promotes binocularity (the child's two eyes working together), visual tracking, and encourages focus and concentration.