Face serum is a lightweight, highly concentrated formulation that penetrates below the skin's surface to deliver active ingredients like vitamin C and hyaluronic acid to the skin. With this targeted approach to skin concerns, serum can often improve your skin's overall appearance more quickly than a cream or moisturizer. Take, for example, Bye Bye Pores 10% Glycolic Acid Serum, which is clinically tested to minimize the appearance of pores in just one week!