Ampoules may just be the best-kept secret in K-Beauty. Byrdie.com even calls it "the one skincare product every Korean woman uses." But how does it differ from regular serums? Peach and Lily creator Alicia Yoon explains the magic kept in those little bottles.

While there are a lot of similarities to serums, ampoules are more potent and targeted, Yoon explained on Byrdie.com. She turned to various K-beauty brands and their product development teams to get the details.

"Most brands said that they will label a product an ampoule if there's a super-high concentration of a specific active ingredient that will help restore, correct, or regenerate the skin," she said.

"When asked how high is considered 'high' when it comes to concentration, they said that though it depends on the ingredient, it's not uncommon to see 50% or more concentration of the star ingredient."

Ampoules are generally packaged in smaller bottles due to this high concentration of product. Usually all you need is a drop or two for your face. Ampoules are also usually light, slippery, and fast-absorbing.

Yoon notes that sometimes brands may use the words "ampoules" and "serums" interchangeably, but ampoules usually contain more concentrated active ingredients.

Yoon also gave tips on different ways you can use ampoules, like "sheet mask sandwiching," where you apply a sheet mask, and before it gets dry you lift it up, pat an ampoule into your skin, and then place the sheet mask back over your face.

"I love the extreme hydration and nourishment I get from doing this-it's perfect after long-haul flights and super-late nights!" Yoon said.

You can also use ampoules to massage your face.

"Because ampoules are a bit more slippery, they make facial massages so silky smooth without any tugging or harsh pulling," Yoon says.

And if your skin is in a really desperate state, Yoon revealed some Korean women layer an essence, ampoule, and serum.

"This might seem like overkill, but every time my skin is a bit dull or dehydrated, this is a super-quick fix," said.

Check out our review of Missha's Time Revolution Night Repair Science Activator Ampoule here.