Aims and Scope of the Book This textbook was written for advanced un­ dergraduate students and beginning graduate students with backgrounds in physical science. Its goal is to acquaint them, as quickly as possible, with the central concepts and some details of transmission electron microscopy (TEM) and x-ray diffractometry (XRD) that are important for the characterization of materials. The topics in this book are developed to a level appropriate for most modern materials characterization research using TEM and XRD. There are, of course, many specialties that have attained a higher level of sophistication than presented here. The content of this book has been chosen in part to provide the background needed for a transition to these research specialties, or to other techniques such as neutron diffractometry. Although the book includes many practical details and examples, it does not cover some topics important for laboratory work. Perhaps the most obvious is the omission of specimen preparation methods for TEM. Beneath the details of principle and practice lies a larger goal of unifying the concepts common to both TEM and XRD. Coherence and wave interfer­ ence are conceptually similar for both x-ray waves and electron wavefunctions.