Over the course of just a few decades, magnetic resonance (MR) has evolved from an analytical tool to a premier imaging mod­ ality. The ability of MR to provide cross-sectional images, as well as chemical and physiological information, has attracted students from many disciplines. Because applied MR is multidisciplinary, it is generally taught in an informal setting rather than as structured course work. During my years of teach­ ing the subject, I felt the need for an appropriate text for students from diverse backgrounds. The materials now available are ei­ ther basic introductions for the lay person or detailed reference resources providing detailed coverage of one or more aspects of MRI. I wrote this book to supplement informal teaching with a text that will provide a detailed conceptual overview. This approach to presenting the concepts will be useful for graduate students in the physical, chemical, and biological sciences who are making the transition to MRI. In addition, medical residents, fellows, and experienced MRI technologists will benefit from this de­ scriptive approach to MRI, which is briefly summarized in the next paragraph. Chapter I, an introduction to the magnetic resonance phenom­ enon, is followed by principles of image formation in Chapter 2.