Many teachers and scholars have written about the importance of inquiry in effective history instruction. At its core, inquiry involves student investigation of a significant historical problem. Experienced teachers, however, often reveal their skill in purposely teaching against the grain. Skilled teachers help students appreciate historical complexity by confronting students' simple, intuitive understandings of the past. Teachers must then think about the common assumptions, often implicit, that students bring to particular historical topics. Teachers also need to recognize historical topics for which there might be no "grain" for students, as well as situations in which teaching against the grain might be detrimental. The teacher's goal should be to help students understand the complexity of the past, and the reality that simple answers are rarely adequate. Teaching is a profession, and like any skilled craft, it takes a lot of work to achieve mastery.