Remaining continually curious about students' mathematical thinking is challenging, yet worthwhile, in teaching practice. This paper describes and analyzes two video-based professional learning (PL) activities designed to help teachers go beyond their initial perceptions of what students understand and to identify what else they might learn about students' thinking. The findings suggest the potential of the activities to evoke different types of curiosity about student-thinking and the conditions that may support such questioning. [For the complete proceedings, see ED630210.]