Along with the entire Montessori method, all used accessories are also the work of Maria Montessori, Italian pedagogue, physician, philosopher and scientist.
Maria Montessori based the development of her method on her own vast body of research. Her research was focused on children and their natural and effortless learning and knowledge acquisition abilities. She discovered, that these abilities are directly influenced by the environment surrounding the kids. She therefore decided to alter the surroundings in a way, that allows the child's mind and senses to get the highest number of inputs, their mind can use to get wisdom and sensory inputs from. This method involved not only the invention of suitable gadgets, but also changing the parent's and educator's approach to the child.
Montessori gadgets are, what you could call "textbooks", with which the baby can grab every concept with both hands, to "lay their hands" on it. Educative value of every gadget is very deep. Every aide isolates one qualitative property, thus making it easy for the kid to master it. These aides help children to learn colors, sounds, music, as well as the basics of future education, like counting, reading, writing, as well as more intricate concepts, which sometimes even the adults don't understand or can't do.
Thanks to their very strong aesthetic quality, the child is drawn to them. Quality of the material almost begs to be handled carefully, softly and with respect and responsibility. Material is constructed in such a way, that the child is aware, when a mistake is made. The baby instantly knows the result and corrects it on its own. With more complex material, acquired experiences and findings are there to help. This way, analytical thinking and independent problem-solving is learned.