What It Is: A powerful anti-aging retinol night serum that helps accelerate skin surface cell renewal to visibly improve fine lines, wrinkles, and deep wrinkles. What It's Good For: This 0.3% retinol night serum visibly reduces fine lines in 5 days** and improves deep wrinkles in 2 weeks*** for a visibly smoother and more youthful appearance. Its innovative packaging isolates a high concentration of pure Retinol powder that is mixed with a lightweight serum to maintain maximum efficacy. Before and After: Results are based on expert grading in a 10-week clinical study: Visibly smooths skin immediately by penetrating up to 15 surface layers deep* Visibly reduces fine lines and wrinkles in 5 days** Visibly reduces deep wrinkles in 2 weeks*** Key Ingredient: Pure Retinol - Kiehl's formula with Pure Retinol helps steadily accelerate skin surface turnover to bring new, fresh skin to the surface to help address visible signs of aging for skin that's visibly renewed and youthful looking. When to Use: Apply once a day at night To Activate: Flip the bottle upside down, remove the bottom cap and set aside Open pouch, twist the retinol capsule onto the bottom of the bottle Push the button down on the capsule to release pure retinol powder Shake vigorously to fully mix the serum Remove and discard capsule, replace with original bottom cap To Apply: Press down on black button 2-3 times for a pea sized drop Gently apply over clean, dry skin Complete your nighttime skincare routine with Kiehl's anti-aging cream for optimal youth-boosting benefits. In the morning, use Kiehl's dark spot corrector and facial sunscreen with SPF 50 for brighter skin clarity. * Based on an in vivo penetration test for retinol penetration ** Based on expert grading in a 10-week clinical study of 71 panelists *** Based on expert grading in a 10-week clinical study of 27 panelists