6 and when the learners themselves invent the concepts (rather than being told about them). This approach to learning is the basis for constructivism. In a constructivist approach the roles of the instructor and students are quite different from those in a traditional class.7 In the approach used in this text, students work together in teams to come to a common understanding of new concepts. 2. Students do not need to be told every detail about every topic. Rather, they need to learn the fundamental concepts. For example, this book does not have information about all 14 Bravais lattices. Rather, it focuses on the cubic crystal systems, with the idea that these systems serve as models from which students can learn the important concepts of crystals. This book can be used in many ways, but was written based on the approach of Process-Oriented Guided Inquiry Learning (POGIL). POGIL was initially developed as a means of teaching general chemistry and has since spread to many other fields. POGIL is used in many different ways, but its basic approach shifts the primary responsibility for learn¬ing from the instructor to the student. There are many resources at the POGIL website (http://pogil.org/), including a detailed Instructor's Guide to POGIL (http://pogil.org/ resources/implementation/instructors-guide). The preface you are reading now describes how I use it in my 100-student Introduction to Materials class. For more details and other tips on how to implement POGIL in your class, you should get the free Instructor's Guide from the POGIL website. In my POGIL class I do not lecture. Rather, students work in teams, typically of four stu¬dents, using the book as their guide. Each section of the text has three primary components: 1) data or information as background material; 2) guided inquiry questions, which are designed to lead the students to understanding the fundamental concepts represented by the data; and 3) application questions (end-of-chapter problems), which provide the students with practice in solving problems using the concepts they have derived. My role is to guide the students, walking around the room and probing them with questions to check their under¬standing. Farrell et al. have described the roles of students within the groups and the class procedures." />