It is a generally aqueous substance of low density that has application in cosmetology. It has the property of quickly penetrating the lower layers of the skin. It usually contains hyaluronic acid. They can exist of two classes. The facial used on the face and capillary.
SERUM (again) low density substance for facial and capillary cosmetological application, allowing it to quickly penetrate the deeper layers of the skin. It is not a moisturizer nor is it greasy like cream.