New emerging disciplines such as Nanoionics and Iontronics are dealing with the exploitation of mesoscopic size effects in materials, which become visible (if not predominant) when downsizing the system to the nanoscale. Driven by the worldwide standardisation of thin film deposition techniques, the access to radically different properties than those found in the bulk macroscopic systems can be accomplished. This opens up promising approaches for the development of advanced micro-devices, by taking advantage of the nanostructural devia- tions found in nanometre-sized, interface-dominated materials compared to the “ideal” relaxed structure of the bulk. A completely new set of functionalities can be explored, with implications in many different fields such as energy conversion and storage, or information technologies. This manuscript reviews the strategies, employed and foreseen, for engineering mass transport properties in thin film ceramics, with the focus in oxide ionic and mixed ionic-electronic conductors and their application in micro power sources.