Transport and retention of water, nutrients, and inorganic and organic contaminants in the environment is greatly affected by physical and chemical processes in porous media such as soils. To definitively understand these processes, multiple scales--ranging from the landscape to the molecular--be investigated. Topics include fractal and spatial heterogeneity, molecular models, in situ spectroscopic and microscopic techniques, and inclusion of time-dependent phenomena in predicting solute transport/retention in soils.