Serums have been around for decades. When skin-care companies started using vitamin C and alpha hydroxy acids (AHAs) in skin-care products, they needed to deliver these ingredients in concentrated ways. Creams just didn't work -- the active ingredients were literally drowning (there was so much water in the products, the vitamins and acids couldn't do their jobs). So serums -- lighter treatment products designed to be layered underneath moisturizer -- were developed. Serums allow a concentrated dose of ingredients to penetrate the skin to fight wrinkles, zap acne, brighten dark spots and so much more.

Most body products are designed to moisturize. And that's it. You have lotions for light moisture, creams for more moisture and balms and butters for the most moisture. Some of these products do contain active ingredients -- designed to brighten dark spots, fight sagging or help with cellulite -- but if the formula is too heavy, the ingredients won't be able to penetrate the skin. And you won't see much of a change -- except your skin will be less dry.

The new generation of body serums has a lighter consistency, potent active ingredients and gives you tons of moisture. Unlike with face serums, you won't need to layer another cream on top of your favorite body serum -- and that's what makes them so easy to use.

The same way face serums address different issues like aging and acne, body serums target specific skin concerns.

The entire line of Vaseline® Intensive Care™ Healing Serums, for instance, offers three different variants. Vaseline® Intensive Care™ Healing Serum Advanced Relief focuses on moisturizing to heal severely dry skin. There's the Vaseline® Intensive Care™ Healing Serum Deep Repair, which moisturizes to soothe cracked skin and heal rough, dry skin. And Vaseline® Intensive Care™ Healing Serum Radiance Restore, which moisturizes to heal and restore dry, dull skin.

One of the best things about a body serum is the incredibly light consistency. Serums are immediately absorbed into the skin so you don't have to wait for them to dry before getting dressed. Vaseline gave our readers free product to try, and here is what they thought:

"It's very light, easy to blend and absorbs quickly into a powdered finish. I hate feeling sticky so that's a big plus from me," says TotalBeauty.com reviewer Thr33things about Vaseline® Intensive Care™ Healing Serum Advanced Relief, SRP $6.79.

"This serum proves that you don't need to use a [thick] lotion [in order to heal] dry skin," says TotalBeauty.com reviewer Val007.

Despite having a light consistency, body serums are able to keep skin feeling hydrated all day -- sometimes even longer.

"My skin felt lightly moisturized, and it really felt like the product soaked in," says TotalBeauty.com reviewer strawberrytime about Vaseline® Intensive Care™ Healing Serum Advanced Relief, SRP $6.79. "The next day, my skin still felt soft."