The molecular basis of evolution is an important concept to understand but one that students and teachers often find challenging. This article provides training and guidance for teachers on how to present molecular evolution concepts so that students will associate molecular changes with the evolution of form and function in organisms. Included are examples that illustrate how mutation followed by selection causes populations to evolve. Next month we will share lab activities that illustrate the concepts and reinforce the complementary roles of mutation and selection in the overall process of evolution.