Can novel 3D models help students develop a deeperunderstanding of core concepts in molecular biology? Weadapted 3D molecular models, developed by scientists, foruse in high school science classrooms. The models accuratelyrepresent the structural and functional properties of complexDNA and Virus molecules, and provide visual and hapticfeedback about biomolecular properties that are often implicitin traditional models. We investigated: 1) Can we measureconceptual growth on core concepts? 2) Do lessons with 3Dmodels improve student outcomes on these measures?, and 3)What factors mediate learning? Model use yielded measurablegains in conceptual knowledge and the greatest gains wererelated to how actively models were used during a lesson andthe facilitative role adopted by the teachers.