The physical properties of superlattices are strongly affected by the chemical and physical properties of the individual layers and by the superlattice structure. In this paper the relationship between structure and properties will be illustrated by the giant magnetoresistance (GMR) effect, as well as the dimensional transitions and pinning mechanisms in respectively magnetic and superconducting superlattices. In the first example we will analyse the effect of the sample structure and interface quality on the GMR of polycrystalline and epitaxial Fe/Cr superlattices grown by molecular beam epitaxy. Secondly, the effect of thermal annealing and ion irradiation on the electrical and magnetic properties of Ag/Fe multilayers is discussed. In a third example, the influence of a very thin Fe interlayer on the coupling phenomena in Fe/Nb multilayers is analysed. Finally, it will be shown that an additional lateral modulation (lattice of submicron holes) in Pb/Ge multilayers substantially changes the critical superconducting parameters.