An overview is given on the non-conventional solid-state processes for the preparation of functional materials. Emphasis is laid on the formation of heterogeneous bridging bonds (HBB) across the boundary between two dissimilar solids under mechanical stressing. Loss of the coordination number for the near surface atoms and/or disturbance of the symmetry of the crystal field or the ligand field are discussed in conjunction with the HBB formation. Case studies on complex oxides, ferrous coordination compounds and some organic - inorganic composites are given.