Nondestructive Evaluation (NDE) is an interdisciplinary branch that is concerned with ensuring the quality and serviceability of materials and structures. The science of NDE incorporates the technology necessary for detection and measurement of significant properties, including discontinuities, in items ranging from research specimens to finished products. By definition, nondestructive techniques are the means by which materials and structures may be inspected without impairment of their serviceability. Using NDE, internal properties of hidden flaws can be revealed or inferred using appropriate techniques. NDE is performed on a wide variety of materials including metals, ceramics, epoxies, wood, fiber glass, and composites. Many types of NDE techniques have been developed; they are differentiated primarily on how they introduce energy into the material and measure the result. The types of energy involved include acoustic (ultrasonic and acoustic emission), electromagnetic (magnetostatic, eddy currents, microwaves, optics, X-rays, and rays), neutrons and heat waves.