Microelectromechanical systems (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 to the fabrication of simple to complex MEMS structures. In addition to its various benefits, one of the unique features of wet chemical-based bulk micromachining is the ability to fabricate slanted sidewalls, such as 45 Degrees walls as micromirrors, as well as freestanding structures, such as cantilevers and diaphragms. This makes wet bulk micromachining necessary 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 includes introductory to advanced concepts and covers research on basic and advanced topics on wet chemical-based silicon bulk micromachining. The book thus serves as an introductory textbook for undergraduate- and graduate-level students of physics, chemistry, electrical and electronic engineering, materials science, and engineering, as well as a comprehensive reference for researchers working or aspiring to work in the area of MEMS and for engineers working in microfabrication technology.