When should I use this serum — morning or evening?

It can be used in the morning or in the evening, because the instructions describe it as a step that fits both a simple morning routine and an evening regimen. The key difference is what follows it. In the daytime, you should apply sunscreen afterward: UV exposure is one of the main reasons skin tone becomes uneven again, so a vitamin C serum is not a replacement for SPF. In the evening, there is no such requirement, and you can use it before your night cream. In both cases, apply the serum to clean, dry skin and wait a moment before applying moisturizer. The formula is designed to layer easily under cream, so you do not need to change your usual moisturizer. If your skin is not used to active cosmetics, start by using the serum a few times a week instead of every day, and observe how your skin reacts. Avoid the eye area. If you are also using acids or retinoids, do not apply all of them at the same time; alternate them on different occasions. If you are pregnant, breastfeeding, have a chronic skin condition or are taking medication, consult a specialist before adding this serum to your routine.