The growth and development of preschool children aged 2-6 is a continuous, unified and complete process. In this process, there are inconspicuous and small quantitative changes, as well as significant qualitative changes. Quantitative change and qualitative change are often going on at the same time, but each has a certain urgent stage. For example, during the entire growth and development process after birth, the head doubles, the trunk doubles, the upper limbs triples, and the lower limbs quadruples. Body shape develops from an oversized head, long trunk, and short limbs at birth to a small head, short trunk, and long limbs as an adult.