Porous materials are omnipresent in sustainable energy and environmental applications. A common physical process in these materials is the flow of (multiple) fluids through their pores; e.g. groundwater contamination by spreading of chemical or microbial pollutants. Current models struggle to capture the dynamics that take place at the microscopic scale, resulting in difficulties to predict large scale flows. This is particularly the case for "complex" fluids: fluids that consist of multiple components or phases and therefore have fluid properties that may depend on the local flow conditions, hence creating complex feedback loops that are poorly understood. This includes multiphase flows with surfactants (e.g. flow of air and water with dissolved PFAS) and particle-laden flows (e.g. suspensions of bacteria). This project will use recently developed 4D X-ray velocimetry method to study the microscopic dynamics of these flows and upscale the findings to arrive at better macroscopic models.