Serums are where a routine actually changes direction. Everything else supports them. This shelf is arranged by concern rather than by brand, so antioxidants, hydrators, retinals, exfoliating acids and brightening formulas all sit side by side, and most people only need one or two of them at a time.

iS Clinical Super Serum Advance+ and Active Serum are our two most-used, and they are not meant to be layered on the same night. Hydra Cool Serum is the hydrating option that suits almost everyone, and Osmosis Replenish MD is the gentler antioxidant for reactive skin. Apply serum to clean, slightly damp skin, before moisturizer. When adding something new, give it four weeks on its own before introducing the next one.