The outer layer of skin can be described as a thin barrier – a kind of film that changes its properties and allows more or less water penetrate its surface, depending on whether the surrounding air is moist or dry. Chemists at the Faculty of Science in Lund have now successfully uncovered the underlying mechanism of how these barrier films control their properties. This is a general mechanism that explains on a molecular level how the skin regulates itself according to the environment but also to the properties of second barrier films, such as in paints, skin creams and food.