The presence of the sea surface microlayer (SML, also called the "skin layer") is a global phenomenon, and because of its unique location, all material and energy exchange between the ocean and atmosphere must occur through this boundary layer. In view of the global relevance of the SML, I will present our research (i) of the DFG Research Unit Biogeochemical Processes and Air-Sea Interaction in the Sea Surface Microlayer (BASS) and (ii) on freshwater fluxes (evaporation minus precipitation) between the ocean and the atmosphere. BASS addresses the extent to which photochemical reactions and microbial communities in the SML process organic matter in unique, previously unknown ways and control the air-sea exchange of gases and energy. BASS will also investigate the coupling between the SML and near-surface water masses, as this coupling determines the distribution of the unique products of bio- and photochemical processes in the SML to the upper ocean. First results include evidence that the SML recovers quickly after a perturbation and reflects 50% more of the incoming solar radiation when there is an excessive accumulation of organic material. The latter is particularly important for our second research focus, i.e., heat transfer and freshwater fluxes. Using salinity anomalies in the SML, I will present results on tracking the fate of precipitation and evaporation processes. We found that salinity and temperature in the SML respond directly to oceanic and atmospheric forcing, and we use this feature to gain a mechanistic understanding of the oceanic water cycle. We have developed and operate an autonomous surface vehicle for field observation and a mesocom facility with precipitation simulator for both research priorities.