Understanding key concepts in molecular biology requires reasoning about molecular processes that are not directly observable and, as such, presents a challenge to students and teachers. We ask whether novel interactive physical models and activities can help students understand key processes in viral replication. Our 3D tangible models are embedded with magnets that accurately represent chemical attractions and, in a study of 492 students, structured model use led to improved understanding of viral replication and self-assembly from pre- to posttest.