Electro-Chemo-Mechanics considers the relationship between electrical, chemical, and mechanical properties of a system. The term is also used for investigations of systems in which all of these three parameters are important, since adjusting one property causes a change of the other two. As we deal with electrochemistry the part Electro-Chemo, i.e. the interaction of chemical potentials with electrical potentials and properties is crucial for any electrochemical cell we investigate. The “Mechanics” part relies to how mechanical strain or mechanically induced deformations influences electrochemistry – and vice versa. In our case, mechanics on the atomic level is important, for example strain induced in thin films by lattice parameter mismatch with the substrate, or strains and lattice deformations induced by defects in materials such as dislocations or associates. Despite such lattice deformations are only a fraction of an atomic distance, they may have a large effect on defect concentrations, defect formation energies as well as the activity of the surface of materials. For example, we measured a factor 1000 difference in oxygen diffusion in (La,Sr)CoO_3-d with the exact same composition, but different mechanic strain states. For characterization of electro-chemo-mechanical behaviour, samples have to be well-defined to allow individual control of all three properties. Our experimental approach using thin films and geometrically optimized model electrodes is therefore ideally suited for the characterization of electro-chemo-mechanical behavior of solids.