Such as, you could come across serums with high concentrations of hyaluronic acid for hydration, niacinamide for even tone and texture, vitamin C for protection and brightening or vitamin E for protection and dampness. If you prefer your retinol in serum type, this La Roche-Posay system is recommended by Kagha. http://www.aunetads.com/view/item-2636539-SOS-WAX-and-Skincare.html