First, Neutrogena Hydro Boost Water Gel became a must-have product for anyone looking for lightweight moisture. And now, Neutrogena Hydro Boost Hydrating Serum, $18, is joining the family. You can layer it under the gel for even more hydration, or you can use it on its own -- it's the perfect barely-there option for summer months.

Not only will Susanne Kaufmann Hyaluron Serum, $182, increase the moisture level in your skin, it will also help it retain that moisture longer while plumping fine lines and wrinkles. The hyaluronic acid in this serum targets the spots that need it most -- so you can say goodbye to dry patches.

Serums are known for being runny and thin, but Peter Thomas Roth Water Drench Hyaluronic Cloud Serum, $65, is anything but. Even though it has a whopping 75 percent hyaluronic acid, it also contains silk proteins that give it a truly cloud-like feel.

SkinMedica HA5 Rejuvenating Hydrator, $178, is so much more than a moisturizing serum. It also has antioxidants -- in the form of flower stem cells -- and peptides to fight aging, and it boosts your skin's own hyaluronic acid production.

A special type of hydrolyzed hyaluronic acid helps PCA Skin Hyaluronic Acid Boosting Serum, $115 (available in April on pcaskin.com), get deep down into the skin to repair wrinkles over time. Meanwhile, ceramides lock in moisture, and niacinamide brightens and protects.