Nondestructive Evaluation (NDE) becomes a key discipline for modem technology. Information about materials defects and properties is significant to guarantee reliability of a product and avoid fatal accidents. For instance technologies with high safety requirements like aviation, automotive, and energy production are driving forces for NDE. Keeping in mind that aging of the infrastructure is an issue in all industrial countries and that, for example, an aircraft can have a lifetime of several decades poses new challenges for NDE and especially nondestructive materials characterization. Besides the traditional in­ field applications, NDE becomes more and more a tool to study materials degradation processes and to provide engineers with input data for sophisticated models describing materials behavior and the life of components. At present, this marriage of NDE and materials modeling shows significant success in predicting damage progression (corrosion, fatigue) and thus an enhancement of availability and reliability of components and complete aircraft. This book will give a snapshot of the present research in materials characterization of aging aircraft. Methods considered are x-ray, ultrasonic, optical and thermal techniques and in particular techniques with high spatial resolution to detect and quantify early stages of degradation or to characterize materials microstructure. Every chapter briefly describes the basics and the principles of one NDE method under consideration. Discussing recent research results by applying these methods completes the chapters. The readers will get an overview of the present state of the art of materials characterization techniques.