When faced with the concept of using a serum as part of the daily skin care routine, most women question the necessity of doing so. Is it important to apply serum, too?

The answer is: Yes. Serums, which are applied after toner and before moisturizer, can address a whole slew of issues that moisturizers cannot. They are specially formulated to target specific concerns like dark spots, wrinkles, and sagging. Because serums are made up of tiny molecules—smaller than those in moisturizers—they are able to penetrate the skin deeper.

If you're still not using a serum as part of your skin care regimen, here are 20 to try.