Materials research plays a central role in the development of microsystems in a number of different ways. More specifically, materials aspects are important issues for both the choice of fabrication method and the design of microcomponents and systems to obtain the desired functions. This book focuses on materials as they are used in microsystems for mechanics (i.e., mechanical sensors such as accelerometers and pressure sensors, and actuators such as micropumps and micromotors) and optics (i.e., optical microcomponents, couplers and switches). Often the materials used are thin films, with thicknesses ranging from fractions of a micrometer to tens of micrometers, and the properties of which usually strongly depend on the details of the deposition process. Researchers discuss this complex interplay between materials, design and fabrication processes. Topics range from exciting MEMS technologies and exotic materials such as diamond-like carbon and aluminum nitride, to various characterization and testing methods and fabrication techniques.