Constructivism has become a widely understood and broadly accepted learning theory. Constructivism contends that each of us makes sense of our world by connecting new experiences to our existing understandings. Learners, as they encounter new situations, attempt to meld incoming information with their existing understandings. Constructivist instructors, in turn, strive to understand students' preexisting understandings (a.k.a. alternative conceptions) and provide learning opportunities that facilitate students' adoption of accepted knowledge (a.k.a. conceptual change). (Contains 2 tables and 2 figures.)