The purpose of this paper is to elaborate the concepts of part and whole in Ference Marton's variation theory for dealing with how learners come to understand something of a whole as made up of its parts. Understanding of the parts and the whole is more difficult than expected; as the whole may have an influence on the parts, the nature of the parts of the whole may differ from that of the parts on their own. As such it is not enough for learners just to know the parts in isolation. They also have to recognize the whole to which the parts refer and how the whole influences the parts. To achieve this, teachers have to provide learners with the experience of variation of the parts and the whole. To demonstrate these concepts, I have applied them to the case of children's learning of Chinese characters in this paper.