Teaching outside one's expertise can be intimidating, but educators can still create an environment where students learn new things. This article provides ways to help educators teach well what they don't know. One way is to consider the principle of backward design. Educators can begin with the end product first: What do they want their students to be able to do as a result of learning in their course? Then outline the kinds of evidence that will be acceptable. Finally, educators can decide what they need to do, and what students need to do, to produce that kind of evidence.