The COSYES project addresses confined molecular systems, encompassing a concept broader than just the spatial cage-like confinement concept and/or pressure-exerted situations, including also solid or liquid environments, interfaces, as well as effects of electromagnetic fields. This project aims to provide a computationally sound and experimentally tractable foundation for the prediction, control, and modification of the properties and the behavior of specific confined molecular systems towards both their fundamental understanding and their useful technological applications (from clean catalysts and photocatalysts to polaronic 2D materials). Methods of choice are first-principles modelling, multi-scale computational simulations, atomistic theory and selected experiments on critical molecular systems under different confinement environments such as the surface of technologically relevant nanomaterials, helium nanodroplets, and the interior of carbon nanotubes,  including  air  exposures  as  a  function of  pressure  and  temperature. This research will be carried out through close collaborations with world-class experimental groups as well as an international network of experts on highly specialised theoretical issues.