Original: It had its foundations in the work of Wilhelm Wundt, Gestalt psychology of Max Wertheimer, Wolfgang Köhler, and Kurt Koffka, and in the work of Jean Piaget, who provided a theory of stages/phases that describe children's cognitive development.
Simplified: Cognitive psychology had its beginnings in the Gestalt psychology of Max Wertheimer, Wolfgang Köhler, and Kurt Koffka, and in the work of Jean Piaget, who came up with a theory of "stages" or "phases" that describe children's cognitive development.