The conditions for water and nutrient uptake by plants are determined by the interaction of the root with its direct soil environment, the rhizosphere. In this DFG-funded project we combine non-invasive 3D imaging with mathematical 3D modeling to decipher the complex hydraulics of the rhizosphere. The combined use of neutron and X-ray tomography allows us to analyze the three-dimensional root architecture, the dynamic water distributions in the root space and the microstructure of the rhizosphere. Our project partners at the University of Stuttgart, working group Prof. Rainer Helmig, integrate this information into a detailed 3D transport model (DuMux). The aim is to transfer time-resolved 3D information for a complete root system grown in the soil (young lupin, maize) directly into a transient 3D simulation model, which calculates the water transport in the soil, the uptake by the root and the transport within the root.