The Blue Retinol Serum for the night regenerates the skin deeply and improves the skin quality visibly and noticeably. In doing so, Biotherm's night serum is a highly effective Bioscience skincare innovation that combines the highest skin renewal rate with a 100% vegan formula. Retinol Serum reduces wrinkles every night, improving skin's evenness and quality for healthy and youthful skin every day.Application: Use the serum with retinol exclusively in the evening. Retinol requires a period of skin acclimation: use twice a week for the first week, then increase frequency to every other night. If discomfort persists, discontinue applications and/or reduce the amount. Always make sure to keep your skin well hydrated. Apply serum every night before your moisturizer. Do not apply to the eye contour or eyelids. Do not use in conjunction with retinol products outside of the Biotherm Blue Pro-Retinol range. Do not intentionally expose your skin to the sun and use a broad spectrum SPF 30+ product daily.