The 10-piece rainbow is part of the Grimm's world of numbers, where games fit perfectly together. Children can discover the more abstract world of numbers in many different ways by playing and by simply using their different senses. They can make sense of what belongs together and thereby discover the world of numbers for themselves.

These are not traditional educational toys or materials that are precise and guide toward one correct answer. None of the products have numbers or fractions on them since the main intention is to provide materials that stimulate free play in various ways. There are endless ways to discover the abstract world of numbers by using the different senses.