SkinCeuticals Serum 20 was designed to restore and protect healthy looking skin. It is lightweight, fast-absorbing and says it neutralizes free radicals. I know that Vitamin C is known to defend against environmental elements. It combines the ferulic acid with 10% L-ascorbic acid which enhances the antioxidant performance (which is very important in this day and time due to all the garbage this is in our environment now). It does help reduce the appearance of fine lines and wrinkles and stimulates collagen synthesis. Once it is absorbed, it can't be washed or rubbed off, so it is effective for at least 72 hours. Great to use with any sunscreen and is ideal for normal or oily skin. I use this daily and it has improved my skin tone immensely. Best to use in the morning after washing your face, I apply 4 to 5 drops on a dry face (also to your neck and chest to help them too). You can follow with your other products or if you want to stay with the same skin care line, I use SkinCeuticals Hydrating B5 Gel and the SkinCeuticals moisturizer that has sunscreen in it. Its clinical studies have been published in respected medical journals and has always been a leader in the field. I did alot of research on the web and then talked to dermatologists and other skin care professionals before investing in it. I highly recommend this product.