Grain growth is the key process in the development of the microstructure of deposited metal films. Grain boundaries in turn exert a dominant influence on the properties of interconnects in integrated circuits. In addition to the practical importance of the phenomena, grain growth in films is of considerable fundamental interest because of the possibility of comparing the predictions of models with observations. The thermodynamic basis for the limiting grain size resulting from grain growth in sheets (or films) was laid by Mullins and subsequently cxtcndcd by Walton et al. to the case of interconnects. In their treatments grain growth stagnates when the forces resulting form the grain boundary excess energy are balanced by the pinning force resulting from grooving. Surface energy anisotropy can drastically modify this equilibrium and even lead to the result that there is no limiting grain size. The basic phenomenology of grain growth in films has been modelled and investigated experimentally. In situ experiments provide a direct comparison with models and confirm many of the predictions based on models. Specifically in the context of lines the effects of grooving on the top and side surfaces are predicted to result in a critical ratio of width to thickness above which a fully bamboo structure cannot be achieved. This is verified by observations.