What Is Microneedling? How It Works, and What It Actually Does to Skin
Microneedling makes temporary openings in the outer layer of skin. The mechanism, the four device types, and where the evidence stops.
Microneedling is a cosmetic technique that uses very fine needles to make temporary openings in the outer layer of skin. Those openings close on their own, and while they are open they are a route past a barrier that normally keeps almost everything out.
That is the mechanism. Everything else said about microneedling is a claim about what follows. Those claims change completely with needle width, with depth, and with who holds the device. This page separates the settled part from the part that is not settled, and marks the line clearly.
What is microneedling, in plain terms
A microneedling device drives an array of short needles into skin, then withdraws them. Each pass leaves a set of narrow openings, usually called microchannels. The skin closes them again.
Two numbers describe any needle, and mixing them up is the most common error in this category.
- Diameter. How wide the needle is, measured in micrometres (µm). One µm is a thousandth of a millimetre.
- Depth. How far the needle travels, measured in millimetres. On an adjustable device this is set by you.
A needle can be very thin and travel far. It can be thick and travel a short distance. Those are different objects doing different jobs, and a single word covers both.
The barrier is the reason this category exists
The outermost layer of skin is the stratum corneum. On facial skin it is commonly given as roughly 15 to 20 µm thick, which is thinner than a sheet of kitchen foil.
It is usually described with the brick-and-mortar model: flattened dead cells are the bricks, a continuous lipid matrix is the mortar. Its job is to keep things out. It does not sort a pathogen from a peptide, and it does not care what your serum cost.
That layer is the reason microneedling exists as an idea. Nothing else in a bathroom cabinet gets past it on purpose.
What sits under it
| Layer | Roughly where it sits | What is there |
|---|---|---|
| Stratum corneum | The first 15 to 20 µm | Dead cells in a lipid matrix. The barrier itself. |
| Viable epidermis | Down to roughly 0.05 to 0.1 mm | Living cells. Melanin is made near its floor. |
| Dermis | Below that, to roughly 0.75 to 1.4 mm on the face | Collagen, elastin, blood supply, nerve endings. |
These are published group means for facial skin. They are not a measurement of your face. Thickness moves with site, age and person, and an eyelid is not a forehead. re:tones publishes the sources for figures like these on its science and mechanism record.
Four different things get called microneedling
The category gets judged as one technique. It is at least four, and they behave nothing alike.
| Type | How it works | Needle | Where it is used |
|---|---|---|---|
| Dermaroller | A drum rolls across skin, so entry is at an angle | Typically 200 µm and wider | Home and clinic |
| Clinical pen | Motorised vertical stamping at treatment depth | Typically 250 µm and wider | Clinic only |
| Dissolving patch | The needle dissolves in skin and carries its payload | No device | Home |
| Home nano pen | Vertical stamping with a fine array | Fine gauge, adjustable depth | Home |
The re:tones MTS sits in the last row. Its needle is 8 µm on the 5D-Nano cartridge and 15 µm on the R-Nano one, with a collar that travels 0.5 to 1.5 mm. It is a cosmetic device, not a medical one, and it is not a substitute for a clinical procedure.
What microneedling does to skin, and what it does not
It does not push product in. The needle opens a route. Whatever crosses does so by diffusion, on its own terms, at a rate nobody has measured for your skin.
It is not an injection. An injection deposits a measured volume into tissue at a known depth. Microneedling does neither. It opens channels and lets what is on the surface meet them. Conflating the two is the fastest way to overstate any device.
A home device is not a clinic appointment. Clinical pens run deeper, on wider needles, in the hands of someone trained to manage what happens next. That is a different procedure with a different risk profile.
Collagen, and the honest version of that story
At clinical depths, practitioners use microneedling with the intent of provoking the skin's own repair response. That is why the category is sometimes called collagen induction therapy. The idea is general dermatological knowledge, not a secret.
Two things get left out of the marketing version. First, a repair response is a response to injury, so it depends on the needle actually reaching tissue that can mount one. Second, the depth and needle width that make that plausible are clinic parameters, not home ones.
re:tones does not claim collagen induction for the MTS. It has run no clinical study and no consumer panel, so it publishes no efficacy percentage, no absorption multiple and no time to result. If a home device promises you a number, ask which study it came from and how many people were in it.
Depth is the variable that changes every answer
Ask what microneedling does and the only correct reply is another question: how deep, and how wide. A 0.25 mm setting and a 1.5 mm setting are not the same activity performed harder.
There is also a gap between a depth you set and a depth that is reached. Skin dents under a tip before it enters, so the dial is a device specification rather than a tissue measurement. That distinction, plus what the published anatomy actually says, is covered in what 0.25 mm to 1.5 mm actually reaches.
The second reason people microneedle: the road in
The first reason is the repair response above. The second is delivery, and it is the simpler argument.
Most of what you apply to intact skin stays on top, dries, and ends up on your pillow. Size is part of it. A widely quoted rule of thumb holds that molecules much above 500 daltons struggle to cross an intact stratum corneum passively. It is a rule of thumb, not a law, and formulation moves it.
A microchannel is a route that does not depend on that rule. That is the whole of the delivery case, and it says nothing about how much of anything crosses. If your interest is absorption rather than needles, start with why your serum is not absorbing.
The MTS is built around that second reason. It releases the ampoule at the moment the needle meets skin, so formula and opening arrive together. The device record draws that coupling in section, and states plainly which parts of the internal geometry the manufacturer has not published.
How long do the channels stay open?
Nobody has published an answer for an 8 µm needle. The closest human evidence is Gupta, Gill, Andrews and Prausnitz, "Kinetics of skin resealing after insertion of microneedles in human subjects", published in the Journal of Controlled Release in 2011. Ten adults, stainless steel arrays on the forearm, barrier recovery followed by electrical impedance.
Uncovered skin resealed within two hours for every needle geometry tested. Under an occlusive dressing it took three to forty hours, and geometry mattered a lot. Those needles were 200 to 500 µm wide and pressed in by thumb, so the figures are context, not a specification for any consumer pen. re:tones states no closure time for its own channels because it has not measured one.
Who should not use a microneedling device
Skip it entirely on active acne, open or broken skin, eczema or psoriasis in flare, sunburn, or over moles, warts and raised lesions.
Skip it if you take oral isotretinoin, or took it in the last six months. Skip it if you scar keloid, or have an active skin infection including cold sores.
If you are pregnant, on immunosuppressants, or being treated for any skin condition, ask your doctor first. Anything clinical belongs with a dermatologist, not with a blog post or a device manual. These products are cosmetics. They are not intended to diagnose, treat, cure or prevent any disease.
How to read a microneedling claim
Three questions sort most of the category quickly.
- Does it separate diameter from depth? A brand that gives one number and calls it the spec is hiding the other.
- Does it state what it has not measured? Absorption rate, channel closure time and needle count are the usual gaps.
- Where did the percentage come from? An efficacy figure without a named study, a method and a sample size is decoration.
Ready to use one at home? The practical safety and technique guide covers cadence, hygiene and the mistakes that cause the problems. If you already know your depth and want the matching formula, the ampoule finder takes six questions.
Frequently asked questions
Does microneedling hurt?
Sensation varies by person, by area and by depth, and it increases as you go deeper. Nobody can promise you a number, and any brand quoting a pain score of zero is describing marketing rather than nerves. Start at the shallowest setting on the widest, most forgiving cartridge and work up over sessions.
Is at-home microneedling the same as what a dermatologist does?
No. Clinical microneedling runs deeper on wider needles, often with topical anaesthetic, performed by someone trained to manage bleeding and infection risk. Home cosmetic devices work in a shallower range with finer needles. They are related techniques, not equivalent ones.
How often should you microneedle?
For a home cosmetic device, once a week is the cadence re:tones specifies, and doing it more often is not faster. Skin needs the gap between sessions more than it needs another session. Stop at the schedule rather than at the feeling.
What depth should a beginner start at?
The shallowest one the device offers, on the widest needle in the box. On the MTS that is 0.5 mm on the R-Nano cartridge. Work up over weeks, never inside a single session, and never on a new area you have not tried shallow first.
Can microneedling make things worse?
Yes, if used on skin that should be left alone. Active acne can be spread by a needle, and dragging the tip instead of tapping is what leaves marks. The contraindication list above exists for that reason, and it is short enough to read every time.
Does microneedling help serums work better?
It opens a route that an intact barrier does not offer. That is a statement about the pathway, not about how much of a given formula crosses, and re:tones has measured no absorption figure for its own products. The mechanism is documented on the science page, including the parts still marked as not claimed.
Related reading: how to repair a damaged skin barrier, what actually changes the look of pores, and the order to apply skincare in.