Students often bring to biology classrooms ideas that are not in line with scientific thought. Simply telling students that their ideas are wrong does not always help advance their scientific thinking. This article describes a teaching and learning activity that allows secondary biology teachers to elicit, interpret, and address students' misconceptions in a meaningful way. The activity provides a chance for students to discuss their nascent ideas about biology with their peers in a safe and nonthreatening environment. More importantly, the activity engages students in a process of reconsidering their initial ideas through reasoning about why certain ideas are scientifically correct.