Hairpedia™

Clear, practical articles about your hair, your routine and the products you use.

Take a closer look at hair.

Explore the fibre you can see, the living structures beneath the scalp and the independent properties that shape how hair behaves.

A closer look, layer by layer.

The visible fibre is made from keratinised cells. Growth and biological activity occur inside the follicle below the skin surface.3

Longitudinal section Diagrammatic — not to scale
Cross-section of a hair fibre, follicle and scalp A simplified longitudinal cross-section showing the hair shaft above the skin, the follicle and bulb below it, surrounding glands, muscle, blood vessels and scalp layers. Use the numbered buttons to read each structure. Keratinised fibre Living scalp tissue Selected detail

Selected structure

01

Hair shaft

What it is
The visible fibre extending above the scalp, made from non-living keratinised cells.3
What it does
Provides the visible length, shape, colour and styling surface of hair.
Why it matters
Friction, heat, light and chemical treatment can change its surface and mechanical condition.
Common misconception
It cannot heal biologically. Products may coat, condition or temporarily improve physical properties, but they do not regenerate living cells.4
Read related Ingredients articles
02

Cuticle

What it is
The outer surface of overlapping, keratinised scale-like cells around the fibre.
What it does
Protects the cortex and influences friction, shine, feel and ease of combing.
Why it matters
Raised, chipped or missing scales increase roughness and expose more of the fibre beneath.
Common misconception
Cuticle scales do not simply “open” and “close” like doors in response to every product.
Read related Concerns articles
03

Cortex

What it is
The main body of the fibre, containing aligned keratin structures and most of its pigment.
What it does
Contributes most of the fibre’s strength, elasticity, colour and mechanical behaviour.
Why it matters
Severe chemical or thermal weathering can extend beyond the cuticle and affect cortical structure.
Common misconception
A cosmetic coating may make a strand feel fuller, but it does not permanently increase the cortex’s biological diameter.
Read related Ingredients articles
04

Medulla

What it is
A central region found in some fibres, particularly thicker ones. It may be absent or discontinuous.2
What it does
Its role in everyday cosmetic behaviour is less central than the cortex and cuticle.
Why it matters
Showing it as variable prevents a simplified diagram from implying that every strand has the same three complete layers.
Common misconception
The presence or absence of a medulla is not a useful at-home score of hair “health.”
05

Hair root

What it is
The portion of the forming fibre contained inside the follicle below the skin surface.
What it does
Moves upward as matrix-derived cells differentiate and keratinise.
Why it matters
It connects the fibre you see with the active structures that produced it.
Common misconception
The root is not the same structure as the follicle that surrounds it.
06

Hair bulb

What it is
The enlarged lower portion of an actively growing follicle surrounding the dermal papilla.
What it does
Contains the matrix region that produces cells for the fibre and inner root sheath.
Why it matters
This is a biologically active growth zone, unlike the visible shaft.
Common misconception
A hair shed with a club-shaped end has not necessarily pulled out the entire living follicle.
07

Dermal papilla

What it is
A specialised connective-tissue structure at the base of the bulb, associated with capillaries and signalling between tissue compartments.1
What it does
Helps regulate follicle development and hair growth cycling.
Why it matters
It illustrates why growth belongs to living follicular biology, not to the shaft.
Common misconception
A product applied to the visible fibre does not directly “feed” the dermal papilla.
08

Matrix

What it is
A population of rapidly dividing cells around the dermal papilla in an actively growing bulb.
What it does
Produces cells that differentiate into the hair shaft and inner root sheath.1
Why it matters
It marks the clearest boundary between active production below the skin and keratinised fibre above it.
Common misconception
The matrix is not present as living tissue along the visible length of hair.
09

Inner root sheath

What it is
A layered sleeve surrounding the developing fibre in the deeper follicle.
What it does
Helps guide and shape the emerging fibre before disintegrating higher in the follicle.1
Why it matters
It shows that the fibre forms within specialised supporting layers.
Common misconception
It is not the same thing as the cuticle on the hair shaft.
10

Outer root sheath

What it is
The outer epithelial compartment of the follicle, continuous with the epidermis.
What it does
Supports the follicle and includes the bulge region associated with epithelial stem cells.
Why it matters
It belongs to living skin biology rather than to the finished fibre.
Common misconception
It is not a removable “coating” around a shed strand.
11

Sebaceous gland

What it is
A gland connected to the upper follicle that releases sebum into the follicular canal.
What it does
Contributes lipids to the scalp and emerging fibre surface.
Why it matters
Sebum level and distribution can affect how quickly the scalp and roots feel oily.
Common misconception
An oil-prone scalp is not, by itself, evidence of poor hygiene or a fixed medical diagnosis.
Read related Concerns articles
12

Arrector pili muscle

What it is
A small smooth muscle attached between the follicle and surrounding dermis.
What it does
Its contraction helps make the hair stand more upright, producing goosebumps.
Why it matters
It is part of the living pilosebaceous unit, not a styling structure in the shaft.
Common misconception
Routine styling cannot permanently “train” this muscle to change fibre pattern.
13

Follicular opening

What it is
The surface opening through which the fibre emerges and sebum can reach the scalp surface.
What it does
Connects the upper follicular canal with the external surface.
Why it matters
Product residue, sebum and scale can collect around surface openings.
Common misconception
Follicular openings do not literally open and close in response to hot or cold water.
14

Scalp epidermis

What it is
The outer skin compartment. Its surface includes the stratum corneum; deeper epidermal layers contain living cells.
What it does
Forms a protective barrier and continuously renews its outer cell layers.
Why it matters
Scalp comfort, scaling and reactions involve skin biology, not damage to the non-living shaft.
Common misconception
Visible flakes do not identify one single cause; several scalp conditions can overlap in appearance.8
Read related Concerns articles
15

Dermis

What it is
Connective tissue beneath the epidermis containing vessels, nerves and much of the follicle.
What it does
Provides structural and biological support to skin appendages.
Why it matters
It houses living structures that cannot be assessed by looking only at the surface of a strand.
Common misconception
Hair-fibre feel is not a direct measurement of dermal or follicular health.
16

Subcutaneous tissue

What it is
A deeper layer containing adipose and connective tissue beneath the dermis.
What it does
Provides cushioning, insulation and structural support.
Why it matters
Deep portions of large follicles can extend towards this layer.
Common misconception
Ordinary rinse-off hair products are not designed to remodel this tissue.
17

Blood supply

What it is
Small vessels and capillaries in living tissue around the follicle and dermal papilla.
What it does
Supports metabolically active follicular cells during growth.
Why it matters
Blood supply belongs to the living follicle environment, not inside the visible fibre.
Common misconception
Cut hair does not bleed because the exposed shaft contains no blood vessels.
18

Pigment distribution

What it is
Melanin produced by melanocytes in the bulb is incorporated into the forming fibre and distributed mainly through the cortex.2
What it does
Contributes to the natural visible colour of the finished strand.
Why it matters
Natural pigment formation and cosmetic colouring act at different biological or physical stages.
Common misconception
Colour deposited onto a finished shaft does not restart pigment production in the follicle.
Read related Ingredients articles
Optional close-upCompare lower-wear and weathered fibre

Weathering is cumulative. Raised, chipped or eroded cuticle features may become more visible with repeated mechanical, environmental, thermal or chemical exposure.4

Reference appearance

Lower-wear fibre

More continuous scale coverage with relatively aligned edges.

Reference appearance

Weathered fibre

Raised, irregular or missing scale areas can expose more of the underlying fibre.

These are simplified reference illustrations, not microscope images or a diagnostic assessment of an individual strand.

Understand your hair profile

Hair is more than one “type.”

Pattern, individual strand diameter, overall density and scalp characteristics describe different things. Any combination is possible, and each can affect how a routine feels and performs.5

This explorer describes the options you select. It does not measure your hair, diagnose your scalp or infer anything from a photograph.

Dimension 01

Pattern

The visible path a strand tends to follow.

Pattern is a useful visual description—not a universally accepted scientific taxonomy. One head can contain more than one pattern, and appearance can shift with length, humidity, styling, chemical treatment and weathering.

View the 1A–4C reference examples
Consumer framework

These labels are common shorthand, not rigid biological categories. The illustrations are reference examples and should not be used to infer ethnicity or determine a product automatically.56

1A

Very straight

Little visible bend. Start light and add control only where needed.

1B

Straight with body

Mostly straight with subtle movement. Distribute product through the lengths.

1C

Straight with bends

Visible bends may need balanced smoothing and flexible hold.

2A

Loose wave

Soft S movement. Lightweight hold helps avoid flattening.

2B

Defined wave

More repeated S-shapes. Apply hold evenly while damp.

2C

Strong wave

Pronounced waves with some loops. Sectioning improves distribution.

3A

Large loops

Broad spirals often benefit from flexible definition.

3B

Springy curls

Repeated loops benefit from even moisture and hold distribution.

3C

Tight curls

Compact loops usually respond best to gentle, sectioned handling.

4A

Small coils

Visible compact coils. Sectioning can support consistent definition.

4B

Angular coils

Tight directional bends. Reduce friction and handle in sections.

4C

Very compact coils

Dense-looking compact bends. Gentle distribution matters more than a rigid label.

Dimension 02

Strand diameter

The width of an individual fibre.

Fine, medium and coarse describe individual strand width—not how much hair is on the scalp. Visual self-assessment is approximate; this explorer does not measure micrometres.

Dimension 03

Density

How closely fibres are distributed across the scalp.

Density is assessed over an area and varies between people and scalp regions. The top-down illustrations use the same area and fibre size so only spacing changes.7

Dimension 04

Scalp characteristics

How the scalp currently feels and behaves.

These descriptions can overlap and change with climate, washing frequency, products and skin conditions. They are not fixed medical diagnoses.

Evidence notes Sources and methodology

Hairpedia™ separates established anatomy from simplified visual explanations and consumer classification frameworks. The anatomy is a schematic learning aid, not a diagnostic image or a scale model.

Pattern, strand diameter, density and scalp characteristics are discussed as separate properties. The profile explorer records no photograph, health information or ethnicity, and its selections are kept only for the current page session.

Web sources were checked on 22 August 2026. Publication and chapter-update dates are recorded below where available.

  1. Anatomy, Hair Follicle. StatPearls Publishing, NCBI Bookshelf; updated 2024. NCBI Bookshelf
  2. Histology, Hair and Follicle. StatPearls Publishing, NCBI Bookshelf; updated 2023. NCBI Bookshelf
  3. Physiology, Hair. StatPearls Publishing, NCBI Bookshelf; updated 2023. NCBI Bookshelf
  4. On Hair Care Physicochemistry: From Structure and Degradation to Novel Biobased Conditioning Agents. Fernandes C et al. Polymers. 2023;15(3):608. DOI: 10.3390/polym15030608. Read the review
  5. How different is human hair? Daniels G, Fraser A, Westgate GE. International Journal of Cosmetic Science. 2023;45(1):50–61. DOI: 10.1111/ics.12819. PubMed record
  6. Worldwide diversity of hair curliness: a new method of assessment. Loussouarn G et al. International Journal of Dermatology. 2007;46 Suppl 1:2–6. DOI: 10.1111/j.1365-4632.2007.03453.x. DOI record
  7. Establishing baselines of hair density measurements. Buontempo MG et al. Journal of the American Academy of Dermatology. 2023;89(6):1294–1296. DOI: 10.1016/j.jaad.2023.08.028. PubMed record
  8. Diagnosis of scalp rashes. DermNet New Zealand; professional dermatology resource. DermNet guidance
  9. How to treat dandruff. American Academy of Dermatology; medically reviewed, updated 2023. AAD guidance

Publication note: The finished illustration and scientific copy should receive appropriate human scientific review before being released beyond the development theme.

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