It's rare to find a skin-care product that shows results almost instantaneously, but the SkinCeuticals C E Ferulic ($166) is one of them. It protects the skin, brightens hyperpigmentation, and maybe even most impressively, works for up to 72 hours after being absorbed. I only added it to my product rotation after trying Madelyn Cline's skin-care routine, and now I'll be savoring every last drop until this bottle is bone-dry.