One of the foremost problems in modeling porous media is capturing the different relevant scales in a problem. The biggest hurdle is how to accommodate the transition from the pore scale to the continuum scale (which is depicted by the dashed line). At the pore scale (and smaller), we can resolve the separate void and solid phases in a material, and the fundamental equations of motion, heat and mass transport, or solid mechanics can be applied. At larger scales, a porous material is treated as a continuum phase, which introduces spatially averaged parameters such as porosity and permeability. Multiscale modeling techniques aim to integrate the various characteristic scales that are relevant to a given transport processes.