When it comes to skin care, the one question we as beauty editors get most often is, What is a serum? Followed by, do I need one? For a beauty product, face serums are strangely complicated: They're in between a moisturizer, an oil and an essence. You apply serums directly to the skin after cleansing, before your moisturizer, in order to deliver potent anti-aging ingredients into your skin. Many are formulated with hyaluronic acid or vitamin C, the same moisturizing and complexion-brightening ingredients we see in moisturizers and other skin-care products, but in stronger, more effective formulas that penetrate deeper into the skin.

Most serums target a specific skin care concern, like sun spots, fine lines, sagging or dull skin. Others tackle multiple problems at once. There is one downside to extra-effective skin care: The price. Face serums use higher quality ingredients and higher concentrations than your daily moisturizer. Plus, it takes a lot of research and development to create a supereffective serum. The good news: As serums grow more popular in mainstream skin care, we've seen drugstore brands launch affordable versions that are as good as the pricier stuff.

Ahead, we're rounded up the best serums across all budgets for treating every skin concern, from wrinkles to dark spots.

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BeautyRX Triple Vitamin C SerumBeautyRx Triple Vitamin C Serum, $95

There's a reason why so many beauty products give vitamin C top billing. This powerhouse antioxidant helps brighten skin and protect against wrinkles and fine lines. Since it neutralizes skin-damaging free radicals, a vitamin C-packed serum means you're working on your skin both present and future. This 10% vitamin C serum contains three forms of vitamin C for triple the antioxidant power. That explains the price tag, but it also means a stronger attack on discoloration and fine lines.

Mad Hippie Vitamin C Serum, $33

Even if you can't opt for the black diamond-level version, vitamin C should still be on your roster for protecting against sun damage and wrinkles. Mad Hippie's cult classic contains konjac root, grapefruit, and chamomile extracts to help soothe and brighten the skin. Notice the product name here isn't something like Glowing Radiant Intensity Fortifying Serum? That's because they're straightforward about what this serum has to offer: Vitamin C-based skin protection with all-natural active ingredients.

Murad Retinol Youth Renewal Serum, $88

If anti-aging is your skin concern, a retinol serum should be the first ingredient on your skin care must-have list. As you work your way up to a prescription-strength retinoid, a more gentle retinol serum is a great place to start. This serum is infused with hyaluronic acid, so you'll avoid the flakiness and irritation that can come from a retinol-based product and go straight to smoother skin.

Neutrogena Rapid Wrinkle Repair Serum, $21.99

You don't necessarily have to drop top dollar or deal in unpronounceable ingredients to tackle fine lines. Neutrogena's take on an anti-aging serum combines ingredients we love like hyaluronic acid, retinol SA, and a glucose formula for an "accelerated" assault on fine lines. If you're looking to drop a few years in time for your high school reunion, this just might be your best bet.