The purpose of this lab investigation is to introduce the concept of osmosis and help students understand “Why Do Red Blood Cells Appear Bigger After Being Exposed to Distilled Water?” This lab investigation will also help students learn how to design a controlled experiment to test alternative hypotheses. The Teacher Notes provide connections to standards, a timeline, safety notes, information on materials and preparation, and instructions for facilitating the lesson and assessing student outcomes. After the Teacher Notes, you will find a Lab Handout and Checkout Questions. Before beginning the lesson, we recommend reading Chapters 1 and 2, which are included in this book selection. Chapter 1 provides an overview of Argument-Driven Inquiry (ADI) with an explanation of what happens during each of the eight stages of ADI, which are the same for every ADI investigation. Chapter 2 focuses on the lab investigations that were designed using the ADI instructional model. The investigations are not meant to replace an existing curriculum but rather to transform the laboratory component of a biology course. This book selection also includes Table of Contents, Preface, Acknowledgments, About the Authors, Introduction, Appendixes, Image credits, and Index.