Hyaluronic Acid

HA is a large sugar molecule made from repeated subunits (polymer) that can be found naturally in our body. Because HA is a polymer, its subunits can be repeated many times or just a few times and thus different molecular weight versions exist. High molecular weight HA are larger molecules, while low molecular weight HA are smaller molecules. The larger the molecule, the more likely for it to stay on the surface to provide surface hydration and to form a protective barrier. 

Dermato-endocrinology, Jul 1, 2012, Hyaluronic acid: A key molecule in skin aging

Journal of Drugs in Dermatology, January 2016, Rejuvenating Hydrator: Restoring Epidermal Hyaluronic Acid Homeostasis With Instant Benefits