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