Clays are nanostructured materials that contain adsorbed water, i.e., water molecules interacting with the solid skeleton. Clay hydration and dehydration is well known to induce important deformations of the material that may end up to instabilities such as desiccation cracking of soils in dry conditions. Cracking of clay-rich rocks can be detrimental (nuclear waste or CO2 storage) or beneficial (oil and gas recovery). Clay desiccation can originate from heating since an increment of temperature induces dehydration and shrinkage. Thermal stimulation is considered as a potential alternative to hydraulic fracturing for shale oil and gas recovery from clay-rich deposits. But the technique is exploratory and its feasibility has to be demonstrated. In this project, we will investigate in detail the physics of thermal expansion of adsorbing microporous media, in particular that of clays, and ultimately assess the feasibility of thermal stimulation of shales. Adsorption in microporous solids is known to induce unusual deformations that can be understood at the molecular scale and captured by thermodynamic integration. Adsorption can induce both shrinkage and swelling depending on the molecular interactions between the fluid and the solid. Accordingly the thermal expansion of adsorbing media can be complex and we propose in this project to study it from the molecular scale to get insight into the physical mechanisms involved. We will investigate various model situations by molecular simulation and derive analytical description of the phenomena from thermodynamics. We will pay a special attention to the physical mechanisms that are relevant for clays. Clays are complex multi-scale materials in which the nanostructure is made of planar micropores where adsorption is structured in layers and induces a swelling orthogonal to the layers, with sharp transitions in function of water chemical potential and temperature. In contrast, macroscopic experiments on clays show continuous thermal deformation with both contraction and expansion, depending on the pre-consolidation state of the material and on the temperature. In this project, we will investigate the thermal expansion of clays from the molecular scale to the macroscopic scale and bridge the gap between the two scales. A fine understanding of the behavior of clay will enable to develop a thermo-hydro-mechanical constitutive modeling with a good predictive ability over a wide range of temperatures and in-situ stresses, relevant for application to thermal stimulation of shales. Finally, this constitutive modeling will serve as a basis for a stability analysis of shale reservoirs and thus to determine the conditions favorable to desiccation cracking. This project is structured as a comprehensive multi-scale approach that involves molecular simulation, thermodynamics and statistical physics, mechanical homogenization and rock mechanics. This project will provide interesting scientific results for the understanding of microporous solids in general and of clays in particular. The project will also have a relevant impact for applications in emerging geotechnical issues involving clays, especially for shale oil and gas recovery.