Miniaturization of mechanical systems promises opportunities for progress of science and technology in new directions. Micromechanical devices and systems are inherently smaller, lighter, faster, and possibly more precise than their macroscopic counterparts. Microfabrication provides a powerful tool for batch processing and miniaturization of mechanical systems into a dimensional domain not accessible by conventional (machining) techniques. Furthermore, microfabrication provides an opportunity for integration of mechanical systems with electronics for closed-loop control to develop high-performance microelectromechanical systems (MEMS). In the most general form, MEMS would consist of mechanical microstructures, microsensors, microactuators, and electronics integrated in the same environment. This paper provides an overview of several MEMS topics including fabrication technology, materials, microsensors, and microactuators.