Thin films formed by physical vapour deposition (PVD) techniques usually consist of columnar grains extending perpendicular to the surface, i.e. parallel to the growth direction. Depending on the growth temperature they undergo a characteristic evolution of their structure: At very low temperatures the grains are isolated from each other by small voids. With increasing temperature the grains are connected by grain boundaries forming a dense solid. With even higher temperatures the grains merge to bigger ones by coalescence and recrystallisation, connected with the loss of their pronounced columnar shape. In the 1970ies it was found that the films structure of different materials can be related to each other by referring the growth temperature to the melting point of the material, i.e. by introduction of the so-called homologous temperature. This means: A film of a material A grown at a certain percentage a of its melting point (i.e. at &alpha•T_m,A) has a very similar structure to a material B grown at &alpha•T_m,B. This finding has been further generalised in the following years with respect to non-thermal energy supply, particularly by energetic ions. At the end, structure-zone models have been set up which show the structure of PVD films in dependence on the homologous temperature and a quantity describing the ion energy. These models are quite general in their validity and enable a good prediction of the film structure. In the talk, the physical processes governing the formation of film structure (shadowing of arriving particles, surface and bulk diffusion and others) are discussed and conclusions are drawn for the formation of appropriate films for particular applications.