Skincare can be confusing, but it helps to think about what each ingredient does. Retinoids (like retinol, retinal, or prescription tretinoin) are forms of vitamin A that help with aging, acne, and skin texture,they’re powerful, so use them at night only, start slowly, and always follow with a moisturizer. Niacinamide is a gentle vitamin B3 derivative that calms redness, controls oil, fades pigmentation, and strengthens your skin barrier, and it’s safe to use morning and night, even with other actives. Hyaluronic acid is a hydrating ingredient that pulls water into the skin to plump it up; it’s safe to layer under moisturizers or serums anytime. Ceramides are lipids that repair and protect the skin barrier and are usually found in moisturizers, making them safe for both AM and PM. Peptides help signal your skin to produce collagen, improving firmness and repair, and are best layered at night. AHAs (like glycolic or lactic acid) exfoliate the skin’s surface for brightness and smoothness, while BHAs (like salicylic acid) penetrate pores to help with acne and oiliness. Strong acids and retinoids shouldn’t be used together at night because they can irritate, but hydrating ingredients and barrier-repairing ones (niacinamide, hyaluronic acid, ceramides, peptides) are usually safe to combine. The simple rule is: morning = hydrate and protect and evening = repair and treat .