Nondestructive evaluation (NDE) is a technique used to probe and sense material structure and properties without causing damage. It has become an extremely diverse and multidisciplinary technology, drawing on the fields of applied physics, artificial intelligence, biomedical engineering, computer science, electrical engineering, electronics, materials science and engineering, mechanical engineering, and structural engineering. Historically, NDE techniques have been used almost exclusively for detection of macroscopic defects (mostly cracks) in structures which have been manufactured or placed in service. Using NDE for this purpose is usually referred to as nondestructive testing (NDT).