Hyaluronic acid is a molecule naturally occuring in all the connective tissues of our body, to which it provides cohesion and appropriate water levels. 50% of our hyaluronic acid is located in the skin. It is one of the most important elements of the extracellular matrix, also comprising proteins such as collagen and elastin, which forms the supporting structure of the skin. Administered through the skin, hyaluronic acid penetrates more or less deeply into the various layers of the skin depending on its molecular weight. The higher the latter, the less it penetrates the skin – it nevertheless provides surface hydration. Hyaluronic acid is made up of two entities of sugars repeated and arranged in a gigantic chain (polysaccharide) with an unequaled capacity to bind and retain water molecules (capable of retaining up to a thousand times its own weight in water!).