Since the first realization of a laser, a multitude of application areas has emerged for this very special light source. One extensive and multifaceted area is material processing. Material processing can refer to both medical applications in eye or heart surgeries and industrial applications for cutting, welding, or hardening various materials. The commonality among these applications is the modification of material through spatially highly concentrated energy in the form of radiation. This ability to concentrate energy distinguishes the laser from conventional tools. The fundamental characteristics of laser radiation are wavelength, spatial coherence, and temporal coherence. The wavelength significantly determines the interaction with a material.