Vitamine C

Vitamin C promotes collagen production, which has the potential to thicken the dermis, diminish fine lines, and is essential for firm, youthful skin. It is an antioxidant, meaning it protects skin cells from damaging free radicals caused by UV exposure.

It also contains a property that inhibits your skin's melanin production, which is what causes skin discoloration like dark spots and hyperpigmentation. Vitamin C can help prevent dark spots from forming in the first place. It's a superior brightening agent that works to fade brown spots without altering normal skin pigmentation. 

The purest form of vitamin C = the better, as Vitamin C actually breaks down when diluted and exposed to light or air. Always keep your serum, cream or powder away from the light.