Successful inquiries using the C3 Framework depend on compelling questions that structure an inquiry and supporting questions that allow the inquiry to unfold coherently. The Inquiry Design Model (IDM) reflects the three elements common in inquiry teaching and learning. Those elements--questions, tasks, and sources--are represented in a one-page "blueprint" that offers a visual snapshot of an entire inquiry such that the individual elements and the relationship among those elements can all be seen at once. In this column, the authors focus on one of those elements--questions--and the distinctions between compelling and supporting questions.