You can use the product once a day either in the morning or at night, but due to the unique formula, we recommend using it at night at the peak of skin cell repair. By using this serum at night, you are helping to boost the skin's antioxidants to help fight the effects of damaging free radicals that your skin is exposed to throughout the day. With continued nightly use, Confidence in Your Beauty Sleep Triple Antioxidant Brightening Serum also keeps working throughout the daytime, continuing to fight the effects of free radicals.