A class of solids (multiferroics) has been considered, in which at least two of the three types of ordering (magnetic, electrical, and mechanical) have occurred. It has been shown that in single-phase materials, the interaction between the subsystems with different ordering is slight, while in composite multiferroics, this interaction is much stronger. This fact makes composite multiferroics promising for the development of a number of devices, in particular, sensors and transducers of magnetic fields.