Pierre Curie's works in the field of crystal physics (on the one-hundredth anniversary of the discovery of the piezoelectric effect)

In connection with the one-hundredth anniversary of the discovery of the piezoelectric effect by the brothers Pierre and Jacques Curie, the history and principal directions of development of the symmetry principle of Pierre Curie, and of subsequent investigations of piezoelectric and related properties of crystals are briefly analyzed in the present note.