With the European Green Deal and its goal to reach net zero greenhouse gas emissions in Europe by 2050, the increased use of the subsurface is inevitable. The large-scale exploitation of the subsurface for storage (e.g., gases) and extraction activities (e.g., geothermal energy) will create large scale perturbations which can destabilize the rock and allow leakage of contaminants into groundwater. Therefore, we need a sound understanding of coupled hydro-geochemical processes arising from such activities, as well as tools to predict these impacts reliably. Reactive Transport Modeling (RTM) has so far proven to be the most powerful tool to track the fate of subsurface contaminants from laboratory up to geological timescales. However, the simplistic approaches to describe the gas-water-mineral interactions in RTM do not accurately capture the complex processes in geological environments, as they do not consider relevant processes that take place at the microscopic scale. These processes need to be upscaled (integrated) into RTM. This requires detailed insights into mineral crystallization processes involving gas in confined porous media, particularly (i) coupled mineral dissolution and precipitation with gas generation and (ii) mineral nucleation at the water-gas interface, since both affect the transport properties and mineralogical reactivity of the rock matrix. Genies will integrate cutting-edge lab-on-a-chip, i.e., miniaturized (microfluidic) experiments with advanced, in operando, micro-analytical techniques and an interdisciplinary environment to provide the insights needed for upscaling. This project will provide high-fidelity experimental datasets that will bring new theoretical insights into hydro-geochemical processes involving gases. The resulting extended RTM will allow reliable modeling of the fate of contaminants and consequently reduce uncertainty when assessing the integrity of subsurface storage and extraction systems.