Conscientious biology teachers continually strive to improve their instructional practices to enhance student learning. At the heart of this goal is a focus on making sure that students understand the biology being taught. One important way to increase focus on teaching that leads to an understanding of biology concepts is by using coordinated and coherent lesson sequences that are based on learning cycles or instructional models. This chapter describes the historical and intellectual roots of the BSCS 5E Instructional Model and how the model can be used to help students achieve a conceptual understanding of biology.