This paper reviews piezoelectric energy harvesting based on vibration. With the development of ultra-low power portable electronics and wireless sensor networks, there is a growing need for unlimited battery life. Energy harvesting is considered as a promising solution for self-powering devices. Piezoelectric materials are particularly effective for converting mechanical vibration into electrical energy. They are categorized into piezoceramics and piezopolymers. Piezoceramics have high electro-mechanical coupling constants but are brittle, while piezopolymers are flexible but have lower coupling constants. The paper reviews key concepts and performance of piezoelectric energy harvesting from vibration, including various types of vibration devices, piezoelectric materials, and mathematical modeling of vibrational energy harvesting. Energy harvesting is defined as capturing and storing energy from surrounding sources for later use. It is also known as power harvesting or energy scavenging. Renewable energy sources like wind, water, geothermal, and solar are considered as future power sources due to the limitations of fossil fuels and nuclear power. However, micro energy harvesting, which generates mW or μW level power, is focused on as an alternative to conventional batteries. This paper focuses on micro energy harvesting. Piezoelectricity is the ability of certain crystalline materials to generate electricity when pressure is applied. This is called the direct effect, while the converse effect is the deformation of crystals when an electric field is applied. The electro-mechanical behavior of piezoelectric materials can be modeled by two linearized constitutive equations. The paper reviews piezoelectric energy harvesting using piezoceramics, discussing various types of vibration devices, single crystal piezoelectric materials, and mathematical modeling of vibrational energy harvesting. It also compares the energy density of piezoelectric energy harvesting devices with electrostatic and electromagnetic devices. The results show that piezoelectric energy harvesting devices have 3-5 times higher energy density than these other technologies.This paper reviews piezoelectric energy harvesting based on vibration. With the development of ultra-low power portable electronics and wireless sensor networks, there is a growing need for unlimited battery life. Energy harvesting is considered as a promising solution for self-powering devices. Piezoelectric materials are particularly effective for converting mechanical vibration into electrical energy. They are categorized into piezoceramics and piezopolymers. Piezoceramics have high electro-mechanical coupling constants but are brittle, while piezopolymers are flexible but have lower coupling constants. The paper reviews key concepts and performance of piezoelectric energy harvesting from vibration, including various types of vibration devices, piezoelectric materials, and mathematical modeling of vibrational energy harvesting. Energy harvesting is defined as capturing and storing energy from surrounding sources for later use. It is also known as power harvesting or energy scavenging. Renewable energy sources like wind, water, geothermal, and solar are considered as future power sources due to the limitations of fossil fuels and nuclear power. However, micro energy harvesting, which generates mW or μW level power, is focused on as an alternative to conventional batteries. This paper focuses on micro energy harvesting. Piezoelectricity is the ability of certain crystalline materials to generate electricity when pressure is applied. This is called the direct effect, while the converse effect is the deformation of crystals when an electric field is applied. The electro-mechanical behavior of piezoelectric materials can be modeled by two linearized constitutive equations. The paper reviews piezoelectric energy harvesting using piezoceramics, discussing various types of vibration devices, single crystal piezoelectric materials, and mathematical modeling of vibrational energy harvesting. It also compares the energy density of piezoelectric energy harvesting devices with electrostatic and electromagnetic devices. The results show that piezoelectric energy harvesting devices have 3-5 times higher energy density than these other technologies.