Effective teaching is the art of getting information to the students' memory in an organized manner to facilitate later retrieval. Thanks to advances in cognitive science, one can talk of the science of teaching. A metaphor that captures the work of effective teachers is "teachers as knowledge engineers," which connotes that effective teachers understand the nature of knowledge and, by extrapolation, the nature of teaching and learning. When teachers take charge of knowledge, view it as a process, and understand how to work with it, they take charge of the knowledge-construction process and better help their students. This article discusses how science teachers use analogies as a means of organizing knowledge in their students' memory. (Contains 1 table.)