Fundamental to the distribution and transport of water, gases and chemical constituents in natural systems are the processes of energy, mass, and momentum transfer. A class of problems offers unique challenges when these processes occur across physical interfaces within the system. Some of the challenges are a result of hard to define interface topologies, abrupt phase transitions, contrasting flow and energy dynamics, difficulties in the characterization of transfer processes, and modeling complexities. The data to study these problems cannot always be obtained from field experiments where multitude of factors contribute to uncertainties of measurements and challenges in characterization of system properties at all relevant length scales. Laboratory experimentation at multiple test scales will continue to play an important and a useful role in addressing these problems and will provide opportunities to improve fundamental process understanding that will lead to new insights for improved conceptualization and numerical models. Examples in multiphase systems as applied to deep geologic storage of carbon dioxide and land/atmospheric interactions are used to show how some of these challenges are addressed through the implementation of theory-driven experiments using multiple test scales.