Two challenges science teachers face are identifying misconceptions students have about how the world operates and getting past those misconceptions. Students' prior conceptions often conflict with the content educators are trying to teach. The gateway to revealing and changing such misconceptions, Fouché says, is predictive questioning. As they plan lessons, good teachers think carefully about misconceptions students are likely to bring--or places where they're likely to get stuck grasping the content--and prepare questions that will elicit prior knowledge, uncover misconceptions, and move students toward the learning goal. Because inquiry-based learning is a socially mediated activity, predictive questioning works best when combined with strategic discourse--students discussing concepts together to come to new understandings. Fouché shows how she used predictive questioning and strategic discourse in an astronomy lesson to bring 12th grade students to an understanding of the concept of dark matter.