It is often both possible and valuable for a teacher to be a researcher in his or her own classroom. This paper describes the nature of cognitive research and focuses on two areas of research that may be of special interest to classroom physics teachers. The first area refers to misconceptions that students bring with them to their physics classes. This part includes the nature of misconceptions, some examples, and implications for classroom teaching with instructional examples. The second area deals with different ways that novices and experts go about storing and accessing information and solving problems. Topics included are expert/novice differences in knowledge organization and problem solving, results of the Hierarchical Analysis Tool (HAT) study, and some implications for the classroom. Discussed are the improvement of instruction, the development of testing instruments, and the necessity of teacher involvement in research.