For best results, it is suggested to use this brightening duo in your regimen. Using the Brightening Complex or Brightening Serum morning or evening is based upon textural preference. Brightening Complex has a more emollient feel, while Brightening Serum is a true-to-form serum and very lightweight. Whichever method chosen of morning and evening application, remember that consistency is key and best results will be found with a full iS Clinical regimen that includes cleansing and hydrating morning and night, along with the brightening duo, and diligent SPF use in the daytime.