As archê, the origin of all being, the Greek mathematician and natural philosopher Thales of Miletus (circa 625-545 BC) referred to water. He was the first to trace the origin and end of the universe back to a single element, stating that "the universe consists of water, whether in solid or liquid form." The majority of the surface of our planet is covered by water. More than 96% of this is saltwater from the world's oceans, while the comparatively small remainder is the precious freshwater that is vital for humanity. Water is life, a scarce resource, a commodity, and a cause of conflicts worldwide: accordingly, the research focuses and areas of expertise of the scientists invited to Heidelberg for the Studium Generale on the topic of 'Water' in the winter semester of 2015/2016 were diverse. Fields represented included engineering, geography, biology, environmental physics, political science, agricultural sciences, and law. In addition to colleagues from Ruperto Carola, speakers from Halle-Wittenberg, Hohenheim, Karlsruhe, and Munich presented their perspectives on the topic.