A review with many refs. As a succinct overview the structure and symmetry requirements of magnetic ferroelec. are discussed. Boracites are the best-studied examples and have phases being simultaneously ferroelec., ferromagnetic and ferroelastic. One of the salient features of such materials is the obligatory occurrence of the linear and bilinear magnetoelec. effects. They represent an invaluable auxiliary information for magnetic symmetry detn. by neutron diffraction. Owing to the complexity of property combinations, work with single crystals and polarized light microscopy is obligatory. Key refs. of the field are given.