Electrically polarized ceramics are classified as electrets, when ions are displaced or dipole moments are aligned in a direction for a considerable period due to an external electric force. An electret can independent irradiate an electrostatic force to the surrounding constituents. We have experimentally proved that hydroxyapatite (HA), the most biocompatible material, is an excellent electret which has desirable biological effects upon surrounding alive and non-alive components in vivo as well as in vitro: Using HA electrets, we have observed that crystal growth from a simulated body fluid can be accelerated or decelerated, and microorganism can be manipulated on the surfaces of HA, depending upon the electric signs.