Sensory material, the probably best known material which has been developed by Maria Montessori. Beyond that it is the most important material for a child's developement, according to Maria Montessori before every successful aquiring of knowledge stands the experience with their own senses. Only with developed and trained senses children can understand certains terms and concepts. They can then put them into context and can therefore sort them into certain categories - this is why Maria Montessori also called it 'the key to the world'.
Because of its strong optical stimulative nature children will be curios and eager to work with the material. Due to the childrens' own inner motivation they gain of knowledge will be effective and lasting.
The material mainly deals with the known 5 senses: touch, hearing, sight, smell and taste. Only when looking closer it becomes evident that through different structures and/or dimensions of the material, it also addresses the sense of balance and body awareness.
For that matter one specific characteristic is isolated with every materials, this helps to not confuse the child and makes it easier for the child to process the impressions.
Additionally every materials inhabits the possibility for error checking, this allows the child to work independently and self-reflective.
Here the principles of shading, pairing and contrast building are being experienced and exercised.