Left: Interfacial water. Right: Schematic of water orientations at the interface to air along with depth-dependent signal contributions. Credit: FHI Researchers from the Department of Physical Chemistry at the Fritz Haber Institute and Freie Universität Berlin have revealed the arrangement of water molecules at the interface between liquid water and air. Their findings help to better understand interfacial chemistry, which is largely determined by the specific arrangement of the water molecules. Published in Science Advances , the study shows that one parameter in particular—one that has been neglected until now—is of fundamental importance: the water twist. Why study the air-water interface? Water is arguably the most important molecule on Earth. Interfaces of water play a critical role in numerous processes within physiology, at the ocean surface, and in the atmosphere. In these processes, it is primarily the incredibly thin region of water directly at the boundary that governs their behavior.…