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Advanced Injection · Facial Anatomy

Filling the right layer:
the 5 layers of facial anatomy and layered injection

Why can filler make a face look “fuller” without making it look younger? Recent research suggests the answer lies in which layer is filled, and which type of gel is used in each layer.

By Dechowat Promda, M.D. · Updated 3 October 2026 · 6 min read

The 5 layers of facial anatomy: skin, superficial fat, SMAS, deep fat and ligaments, and bone
The 5 layers of the face and the type of treatment suited to each

At a glance

  • The midface has two layers of fat. The deep layer supports the structure, while the superficial layer moves with your expressions and shapes the face when you show emotion.
  • A 2026 paper proposes “balanced restoration”: filling both layers in balance, rather than only the deep layer.
  • Firm gels suit the deep layer. Placed in the superficial layer, they can make the face look overfilled when you smile.
  • The skin layer needs its own kind of care, such as skin boosters injected into the skin.

The face has 5 layers

From the surface down to the bone, the face is arranged in these layers: skin, superficial fat, the SMAS (a layer of fascia and muscle), deep fat with the retaining ligaments, and bone with its covering (periosteum). With age, every layer changes at the same time: bone thins, deep fat deflates and ligaments loosen, so the skin above sags with them.

Tap through each layer in the 5-layer illustration on our home page.

Two fat layers, two roles

A paper by Rohrich and colleagues, published in Plastic and Reconstructive Surgery Global Open in 2026, explains that the midface has “two fat layers with different shapes and mechanical properties”1.

Fat layerExample fat compartmentsRole
Deep (beneath the SMAS, against the periosteum)Medial and lateral SOOF, deep medial cheek fatStable; supports the structure and the layers above
Superficial (between the SMAS and the skin)Infraorbital, superficial medial and middle cheek, nasolabial fatMoves with expression; shapes the face when you show emotion

The authors propose balanced restoration: assessing and filling both layers in balance, instead of the traditional approach of filling only the deep layer. They report that this uses less gel and gives more predictable results1. During the examination, a gentle pinch of the skin (the pinch test) helps tell whether it is the superficial or the deep fat that has deflated. If the skin is thin, creases and is slow to spring back, the loss is usually in the superficial fat1.

Matching the gel to the layer

Each gel differs in firmness (its G′ value), cohesiveness and elasticity. The same paper recommends:

  • Deep layer: a gel with moderate to high G′ and good cohesiveness, to support the structure
  • Superficial layer: a flexible gel that moves well with the face. The authors state that firm, less stretchy gels are “not suitable for placement” in this layer, because the face looks overfilled when it moves1.

This is why some people look good at rest after filler but look odd when they smile. The problem is not only the amount, but the type of gel and the layer it is placed in.

The skin layer and skin boosters

The top layer is the skin itself, and filler does not improve skin quality. A 2024 study in Clinical, Cosmetic and Investigational Dermatology injected polynucleotide (PN) into the skin of 30 Asian volunteers, 3 times at 4-week intervals. At the 6-month follow-up, 43% were rated as very much improved and 33% as much improved in smoothness, firmness and radiance, with no side effects found during follow-up2.

Limitations: this study had no control group and a small sample. Most of the evidence for PN skin boosters is still at this level, so it should be seen as an interesting early result, not a final conclusion.

Read more about skin boosters.

What this means in practice

  1. Assess layer by layer, from the bone structure through the deep fat and superficial fat to the skin.
  2. Choose the gel and the instrument to match each layer, rather than using one product for the whole face.
  3. Use only as much as is needed, and review the result before adding more.
  4. Plan for safety around the blood vessels in each area. Read more in our article on safety.

References

  1. Rohrich RJ, Cetto R, Gallagher CJ, Weir D, Hollander DA, Brown J, Wu K. Balanced Restoration: Optimizing Midface Rejuvenation Using Hyaluronic Acid Fillers. Plastic and Reconstructive Surgery Global Open. 2026. pmc.ncbi.nlm.nih.gov
  2. Lim TS, Liew S, Tee XJ, Chong I, Lo FJ, Ho MJ, Ong KT, Cavallini M. Polynucleotides HPT for Asian Skin Regeneration and Rejuvenation. Clinical, Cosmetic and Investigational Dermatology. 2024. 2024;17:417–431. doi:10.2147/CCID.S437942

This article is for general information and is not personal medical advice. Always consult a doctor before deciding on any treatment.