This paper draws attention to the literature in the areas of learning, specifically, constructivism, conceptual change and cognitive development. It emphasizes the contribution of such research to our understanding of the learning process. This literature provides guidelines for teachers, at all levels, in their attempt to have their students achieve learning with understanding. Research about the constructive nature of students’ learning processes, about students’ mental models, and students’ misconceptions have important implications for teachers who wish to model scientific reasoning in an effective fashion for their students. This paper aims to communicate this research to teachers, textbook authors, and college professors who involved in the preparation of science teachers. This paper is divided into two major parts. The first part concentrates on a critical review of the three most influential learning theories and constructivist view of learning and discusses the foundation upon which the constructivist theory of learning has been rooted. It seeks an answer to the question of “What are some guiding principles of constructivist thinking that we must keep in mind when we consider our role as science teachers?.” The second part of this paper moves toward describing the nature of students’ alternative conceptions, the ways of changing cognitive structure, and cognitive aspects of learning and teaching science.