In Montessori, we recognize that there are four stages, or planes, of development for all humans which require extraordinary efforts and inevitable regressions before we are virtually reborn into the next. They are markedly distinct from one another and they are important to understand when we look at designing an environment and teaching strategies to meet the physical, cognitive, and spiritual needs of each.
Today we'll look at the first plane, ages 0-6.
This plane can be broken up further into two subsets, 0-3, in which learning is unconscious, and 3-6, where children become susceptible to direct adult influence. We consider the mind of the child in this plane to be "absorbent", learning about the world around them primarily through the senses.
Montessori teachers trained in this age group place great importance on preparing the classroom environment with carefully selected "materials" (you could easily call them "toys") that lend themselves to exploration. The teachers encourage the children to freely move within this environment, trusting that the children will be drawn by instinct to engaging with the materials and with each other in a way that best supports their individual needs for growth.
Since the children are learning from everything they are in contact with at this age, the teacher is well aware that as a constant "on stage at all times" role model, the children are likely to copy his/her behavior and actions. The children do not need to be externally rewarded for their learning. The desire to grow up is plenty enough reward. The teacher's primary role in the classroom is not to shuffle the children through mastery of a series of skills but to step back, observe, and aid these natural desires.
Chapter 3 of The Absorbent Mind: The Periods of Growth, pages 18-28 (aff)
This article from Montessori Northwest is very well written and worth a read.
For insight into the two charts designed by Maria Montessori to illustrate the four planes, read this article by Camillo Grazzini printed in the NAMTA journal