Being a millennial, there are lots of things we did as teenagers that now we know we got wrong.

In addition to the myth that moisturizers made our skin greasy or the thought that tanning beds killed pimples (wut?), there also was the thought that toner was a benign skin care step.

Today, we’re all grown up, and I am here to say that toner is one of the best things you can do for your skin. Some dermatologists say toners aren’t necessary, but not all toners are created equal.

Let’s break it down.

When I say “toner,” you might think of the old-fashioned toners we used as teens. These usually were a mixture of alcohol, water and witch hazel that sometimes said “astringent” on its label. They were meant to “shrink” pores, but pores are not windows – they don’t open and close. The high alcohol content of these “toners” would actually just dry the living hell out of your skin and, in turn, make your skin produce even more oil to compensate.

Also, toner sometimes referred to a mix of water and glycerin used to “get the last bits of makeup off your face.” However, as we grew up, we realized that cleansing actually should clean your skin and get off all of your makeup. If there’s still makeup on your skin after cleansing, you need to cleanse better or get a different cleanser. (Try double-cleansing.)

When I talk about toner, I’m referring to the K-beauty (Korean beauty) notion of toner, which is the second step of skin care and helps prep the skin. Remember that (for the most part) skin care should be applied from thinnest to thickest. Toner is a liquid and therefore comes first after cleansing.

Skin care queen Caroline Hirons once referred to toner as a condiment on your sandwich: “Yes, you can make a sandwich using just bread and ham/cheese — but how much better does that sandwich work with butter or mayo? It binds it all together and facilitates the process.”

Toners come in all different formulations, but they should serve these basic functions.

Toners should balance. They help reset the pH balance of your skin, which ideally sits at a slightly acidic 5.5. In the very basic sense, our skin’s pH is its balance between being very oily and very dry.

Your skin is a protective organ, working to keep all good stuff in and bad stuff out. If that barrier is disrupted, it can’t do its job. Even though most cleansers today are formulated to be pH-balanced, cleansing (with any cleanser) will still trip up your skin’s pH level. Think of how you condition after shampooing your hair – toner is like your skin’s conditioner to balance it out and make it look and feel moisturized and soft.

Now, don’t get me wrong: like any other function, our skin is able to balance itself out and will do so. Though, it’s going to take more than twice as long for it to naturally do this and, in that time, your skin will start to overproduce oil in oily skin and further dehydrate in drier skin types. Just use the toner and save yourself the hassle.

Toners also should hydrate. Our skin is constantly parched thanks to the weather, our dry offices, central heating and air conditioning, travel, pollution, etc. (Not to mention drinking, smoking, caffeine and more lifestyle choices we make that suck our skin dry.)

A good toner will act as a humectant, which means it pulls in moisture from the air and traps it in the top layers of the skin. Since toners are liquid, their molecules are smaller and can penetrate deeper into the skin for better hydration. For instance, the K-beauty “7 Skin Method” entails applying seven layers of a hydrating toner to front-load hydration. For people with very dry skin, I always recommend using a hydrating toner in addition to their creams and oils.

Finally, toners should help the rest of your skin care penetrate. Toners also will help in the absorption of products that follow. When your skin is prepped and hydrated, everything applied after will penetrate deeper.

When using any of these hydrating toners above, they usually come in a spray bottle or a tube with a little opening. I like to pat them right onto my face. For hydrating toners, look for ingredients such as hyaluronic acid, glycerin, algae or aloe vera — anything hydrating and softening.

There’s another type of toner typically used after cleansing: exfoliating toners.

We’ve talked about it before, but acids come in all forms, from creams and lotions to serums and liquids. Acids in toner form are created with alpha hydroxy (AHA), beta hydroxy (BHA) and/or poly hydroxy (PHA) acids. I believe they are the most effective way to exfoliate and resurface your skin without using a traditional sugar scrub that can cause microtears and damage to your skin. These toners are the exception to the no-alcohol rule, mostly because you need alcohol to suspend certain acids. When using an acid toner, I usually apply it with a cotton square in upward strokes.

If I’m using an acid toner, I also apply my hydrating toner afterward. Then, I go in with my serum/moisturizer/oil or whatever I am using next.

There are hundreds of great hydrating (and acid) toners on the market, but your toner step is not limited to just those that say “toner” on the label. As long as it has hydrating properties, you can use your favorite mist (Tatcha Luminous Dewy Skin Mist is my toner step) as well as certain kinds of essences (I’ll get into it another day, but it’s basically a thinner serum).

Get yourself a proper toner and level up in adulthood.