Abstract: Recent advances in molecular modeling methods and nano-scale measurements of material properties offer a new paradigm for understanding the multi-scale behavior of complex natural materials such as clays. Recent studies at MIT have used molecular models to simulate the hydration of montmorillonite and to predict elastic properties at different hydration states. We have also used molecular models to investigate the interactions between clay platelets and hence, to develop the first meso-scale models of clay aggregates. Future research will extend these analyses to include distributions of particle sizes and different clay minerals. The long-term goal is to use the bottom-up approach to improve macroscopic models of clay behavior.