A class of microsystems that combine the functions of optical, mechanical, and electronic components in a single, very small package or assembly. MOEMS devices can vary in size from several micrometers to several millimeters. MOEMS may be thought of as an extension of micro-electro-mechanical systems (MEMS) technology by the provision of some optical functionality. This optical functionality may be in the form of moving optical surfaces such as mirrors or gratings, the integration of guided-wave optics into the device, or the incorporation of optical emitters or detectors into the system. The term may be confused with micro-opto-mechanical systems (MOMS), which more properly refers to microsystems that do not include electronic functions at the microsystem location. MOEMS is a rapidly growing area of research and commercial development with great potential to impact daily life. The basic concept is the miniaturization of combined optical, mechanical, and electronic functions into an integrated assembly, or monolithically integrated substrate, through the use of micromachining processes derived from those used by the microelectronics industry. These processes, utilizing microlithography and various etch (subtractive) or deposition (additive) steps on a planar substrate, enable the production of extremely precise shapes, structures, and patterns in various materials.