Piezoelectric energy is drawing attention as the upcoming energy source. It is converting a little mechanical energy such as force, pressure and vibration that we may easily ignore into electric current and voltage. Piezoelectric harvesters can be employed as battery rechargers in various environments, such as industries, houses, the military and handheld or wearable devices. The possibility to avoid replacing exhausted batteries is highly attractive for wireless networks, in which the maintenance costs due to battery check and replacement are relevant. Another emerging field of application is biomedical systems, where the energy could be harvested from an off-the-shelf piezoelectric unit and used to implement drug delivery systems or tactile sensors. Recent research also includes energy conversion from the occlusal contact during chewing by means of a piezoelectric layer and from heart beats.