“As I’ll suggest in chapter 10, you might want to have two types of serums—one for the morning and another for the evening. Each one will contain slightly different ingredients. There will be more UV-combating ingredients in the daytime serum and more retinol in your nighttime serum. Serums are not heavy and moisturizing, as your daytime moisturizer or nighttime face cream should be. Rather, serums are light, fast-absorbing, and packed with potent ingredients that provide your skin with lasting long-term benefits.”