Chemistry can be a very difficult topic for students to understand, in part because it requires students to think abstractly about the behaviors and interactions of atoms, molecules, and ions. Visualizations in chemistry can help to make chemistry at the particulate level less abstract because students can actually "see" these particles, and dynamic visualizations can help students understand how these particles interact and change over time as a reaction occurs. The chapters in this book are divided into four categories: Theoretical aspects of visualization design, design and evaluation of visualizations, visualizations studied by chemical education researchers, and visualizations designed for the chemistry classroom. Chapters 2-4 of this book focus on theoretical issues and concerns in developing and using animations and simulations to teach chemistry concepts. The theoretical frameworks described in these chapters not only include learning theories [such as Behaviorism, Cognitive Load Theory, and Vygotsky's Zone of Proximal Development], but also describe design principles that are informed by educational research on learning with multimedia. Both of these frameworks can be used to improve the way dynamic visualizations are designed, created, and utilized in the chemistry classroom. Chapters 5-8 of this book provide two examples of paired articles, in which the first chapter introduces and describes how the dynamic visuals were designed and created for use in chemistry instruction and the second chapter describes a chemical education research study performed to evaluate the effectiveness of using these dynamic visuals for chemistry instruction. Chapters 5 and 6 focus on interactive simulations created as part of the PhET Interactive Simulations Project. Chapters 7 and 8 focus on the virtual-world program Second Life and how it is being used to teach chemistry lessons. Chapters 9-14 of this book describe the results of chemical education research studies on the use of animations and simulations. Chapters 15-17 describe how specific dynamic visualization programs and modules were designed and how they should be utilized in the chemistry classroom to improve student learning.