Fog and low cloud systems are an extraordinary laboratory to better understand fundamental dynamics of water, energy, and biotic interactions. These dynamic phenomena connect Earth systems at multiple spatial (droplet to synoptic) and temporal (seconds to decadal) scales and have led to multi-disciplinary research cross-connections. Scientific breakthroughs from fog and fog-related studies inform the water and energy resource communities, atmospheric science generally, and produce cascading knowledge benefits applicable to weather forecasting, agriculture, public health, and natural resource management. Fog droplets scatter light, transport water and aerosols, and enable the long-range deposition of microbes across hundreds of kilometers. These and other low-cloud processes influence ecosystem functions, the surface energy budget, and biochemical interactions. This session explores the recent interdisciplinary advances in our understanding of fog and marine and coastal low clouds as a system and examines future changes and their impacts. We invite submissions on observations, modeling, prediction, and theory.