Chemistry Education Research (CER) is concerned with teaching and learning in chemistry, investigated through a variety of qualitative and quantitative methods. Researchers in chemistry education explore a broad range of areas, including the mechanisms by which students construct understanding of chemistry principles and the barriers that impede construction; the development of instruments that measure understanding, attitudes, identity, and other affective constructs; how evidence about student learning can be incorporated into curriculum design; and how to measure the impact of curricular transformations. It is important to emphasize that CER, and discipline-based education research (DBER) more broadly, is grounded in the “priorities, worldview, knowledge, and practices” of the discipline being studied. However, while a deep knowledge of chemistry principles is vital, it is not sufficient: an understanding of the methods and principles of science education, educational psychology, and cognitive science are also necessary. Chemistry education researchers are uniquely qualified to think deeply about what expertise in chemistry looks like and how it might be developed.