Abstract: Vibration Energy Harvesters are emerging devices that are able to scavenge otherwise wasted energy from ambient vibrations. In the last years, vibration harvesters have been proposed for a large number of applications, such as industrial applications, medical implants, embedded sensors in buildings and bridges and regenerative shock absorbers. In particular, in the future, vibration harvesters could be fundamental for the development of Internet of Things applications and for Industry 4.0 revolution. The performances of Vibration Energy Harvesters are strongly affected by the variability of the applied mechanical excitation source from which energy is harvested. When the vibration characteristics change with time, also the optimal operating point of the system changes with time. Such an optimal operating point is characterized by the highest value of the extracted electrical power and it is called Maximum Power Point (MPP). Hence, due to the time varying nature of the vibrations characteristics taking place in nearly all practical cases, MPP Tracking (MPPT) is mandatory in order to avoid the waste of precious available energy. In order to connect Vibration Energy Harvesters to DC electronic loads the rectification of their AC output voltages is needed. AC/DC power electronic interfaces can be passive or active. In this presentation, MPPT techniques for both passive and active AC/DC architectures will be presented and discussed.