Serum

A serum is a lightweight treatment with a higher concentration of active ingredients than most moisturizers. Where a moisturizer mainly hydrates and protects, a serum targets a specific concern, such as dark spots, fine lines, loss of firmness, enlarged-looking pores, or dullness. Its light texture layers easily under the rest of your routine. Using a serum consistently is one of the easiest ways to focus on a specific concern.

Both are concentrated treatments, and the terms are often used interchangeably. In Korean skincare, an ampoule usually refers to a more intensive formula with a higher amount of a key ingredient, while a serum is typically designed for steady, everyday use. Most go after toner and before moisturizer. Some ampoules, such as exfoliating ones, are massaged in and then rinsed or wiped off, so always check the directions.

Start with the concern that matters most to you. For dark spots and uneven tone, look for tranexamic acid, kojic acid, niacinamide, or vitamin C. For fine lines and firmness, choose peptides, calcium complexes, or retinoids. For pores and texture, exfoliating serums with AHA or BHA and zinc work well, while hyaluronic acid suits any skin that needs more hydration. Many people use two serums for two concerns, one in the morning and one at night.

It depends on the ingredients. Antioxidant and brightening serums like vitamin C work well in the morning under sunscreen. Exfoliating serums, retinoids, and more intensive treatments are usually best at night, when skin is not exposed to the sun. Hydrating and firming serums can be used twice a day, after toner and before moisturizer. Always follow a morning serum with sunscreen.

Yes, layering two serums is common, especially when you want to address more than one concern. Apply the thinnest, most watery serum first and give it a moment to settle before the next. Avoid stacking several strong actives, like exfoliating acids, retinol, and vitamin C, in the same routine. Rinse-off exfoliating ampoules are used on their own before the rest of your routine, not layered with a leave-on serum. A simple option is one serum in the morning and a different one at night.

In most cases, yes. Serums are designed to target a concern, while moisturizers seal in hydration and support the skin barrier, so skin stays comfortable and does not dry out. Very oily skin may get by with a hydrating serum alone in humid weather, but most routines work best with both. Apply the serum first, then follow with moisturizer.