The formation of a ferroic order is always associated with the breaking of a symmetry. For example, the symmetry of spatial inversion is broken when ferroelectrics develop their electric dipole moment, and time reversal is broken when ferromagnets become magnetic. The symmetry breaking can be described by an order parameter, the polarization P and magnetization M in these two examples, and leads to multiple equivalent ground states which can be selected by the appropriate conjugate field; electric or magnetic for ferroelectrics or ferromagnets respectively. This leads for example to the familiar switching of magnetic bits using magnetic fields in magnetic data storage.