So, what exactly is a serum? “A serum is usually a liquid or gel containing high concentrations of skin actives, which are able to penetrate deeper than other topicals [like moisturizers] with content occlusives that prevent deeper penetration,” explains board-certified dermatologist Dr. Marnie Nussbaum.

In other words, a serum is a skincare product applied to the skin with the intent of delivering very powerful ingredients directly into the skin. Serums are particularly suited to this task as they’re made up of smaller molecules that can penetrate deeply and deliver a very high concentration of active ingredients.

This makes a serum a great tool for targeting specific skincare concerns such as fine lines, not so fine lines and skin conditions such as psoriasis, rosacea, acne, eczema and dermatitis. Hello lovely youthful clear skin!