This amazing humectant holds one thousand times its weight in water. You can think of Hyaluronic Acid as a wafer sponge that fills and plumps out your skin.
As an ingredient in skincare, it is unfortunately too large a molecule to travel into the dermis of the skin- so it sits only the surface layer or the epidermis, where it is a good moisturizing ingredient.
You will also see a lot of FDA-approved injectable Hyaluronic Acid products on the market, given as wrinkle treatments at dermatologist and plastic surgeon's offices. These are marketed under the names of Restylane® and Juvederm®.