Piezoelectrics are materials that exhibit the piezoelectric effect; this means that they produce electricity when stressed (i.e. squeezed)
Piezoelectrics are named after the greek word "piezo", that means ‘press’, and electricity. Piezoelectricity can be found in quartz (SiO2) crystals, in some synthetic ceramics such as barium titanate (BaTiO3) crystals, in zinc oxide (ZnO), and even in collagen fibrils that are present in bones!