MEMS-based sensors and actuators have become remarkably popular in the past few decades. Rapid advances have taken place in terms of both technologies and techniques of fabrication of MEMS structures. Wet chemical–based silicon bulk micromachining continues to be a widely used technique for the fabrication of microstructures used in MEMS devices. Researchers all over the world have contributed significantly to the advancement of wet chemical–based micromachining, from understanding the etching mechanism to exploring its application for the fabrication of simple to complex MEMS structures. Apart from various benefits of wet chemical based bulk micromachining, one of its unique features is the ability to fabricate slanted sidewalls like the 45° walls as micromirrors as well as freestanding structures such as cantilevers and diaphragms. This makes wet bulk micromachining inevitable for the fabrication of structures for myriad applications. This book provides a comprehensive understating of wet bulk micromachining for the fabrication of simple to advanced microstructures for various applications in MEMS. It incorporates introductory to advanced concepts and thus would serve as a textbook for undergraduate and graduate-level students as well as a comprehensive reference for researchers working or aspiring to work in the area of MEMS. © 2017 by Pan Stanford Publishing Pte. Ltd.