This book presents the fundamentals of crystallography to students studying the solid state in chemistry, physics, materials science, geological sciences, and engineering. Computers are an essential part of crystallography, and appropriate computer-based exercises are integrated into this book for self-study. The material is presented in a logical order with the goal of understanding not only how atoms are arranged in crystals, but how crystal systems are related to each other. The theoretical material is developed extensively in two dimensions. An overview and some detailed examples are given in three dimensions.