This paper reviews the state-of-the-art in vibration energy harvesting for wireless, self-powered microsystems. It discusses the characteristics and transduction mechanisms of inertial spring and mass systems, including piezoelectric, electromagnetic, and electrostatic generators. The paper presents the characteristic equations for inertial-based generators and the damping equations for the three main transduction mechanisms: piezoelectric, electromagnetic, and electrostatic. Each mechanism is detailed with specific examples and applications, such as impact-coupled, resonant, and human-based devices. The paper also covers the design considerations for maximizing power output, including the importance of matching the generator's frequency and damping to the application environment. Additionally, it explores the use of piezoelectric materials in various applications, such as shoe-mounted generators and in vivo energy harvesting, and the development of cantilever-based piezoelectric generators. The paper concludes with a discussion on the suitability of different techniques for energy harvesting.This paper reviews the state-of-the-art in vibration energy harvesting for wireless, self-powered microsystems. It discusses the characteristics and transduction mechanisms of inertial spring and mass systems, including piezoelectric, electromagnetic, and electrostatic generators. The paper presents the characteristic equations for inertial-based generators and the damping equations for the three main transduction mechanisms: piezoelectric, electromagnetic, and electrostatic. Each mechanism is detailed with specific examples and applications, such as impact-coupled, resonant, and human-based devices. The paper also covers the design considerations for maximizing power output, including the importance of matching the generator's frequency and damping to the application environment. Additionally, it explores the use of piezoelectric materials in various applications, such as shoe-mounted generators and in vivo energy harvesting, and the development of cantilever-based piezoelectric generators. The paper concludes with a discussion on the suitability of different techniques for energy harvesting.