Retin-A and other retinoid products fight signs of aging like wrinkles and age spots by increasing cell turnover and stimulating the production of new collagen. In short, they’re an anti-aging marvel. But if you want to get the most of your retinoid, you shouldn’t use it in the morning—it’ll just go to waste. When you step outside, the sun will immediately start deactivating your precious potion. Save your time and money and put it on before bed.