This chapter introduces structuralism from several different angles. In the first section, the concept of structure (and in extension those of schema, pattern, gestalt, etc.) will be contrasted with that of function (and in extension those of activity, interaction, transformation, etc.). Such a comparison will not merely reconfirm the old dichotomy as introduced into psychology by James and Titchener, but will emphasize the mutual dependence of structure and functions. In this attempt I rely on Piaget's interpretations and, thus, emphasize genetic aspects. Reference will also be given to recent trends in linguistics, especially to Chomsky's transformational grammar.