Hair Growth 101
Follicle, shaft and the cycle underneath it all.
Last reviewed by the Hairavie editorial team on September 1, 2026.
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The follicle is alive. The strand isn't.
Hair is produced inside the follicle, a small structure in the skin. Cells divide there, fill with keratin and harden as they move upward.
By the time the fibre leaves the scalp it is no longer living tissue. That single fact explains most of hair care: what happens at the follicle is biology, and what happens to the strand is physics and chemistry.
Three layers of a strand
- Cuticle — overlapping outer scales that protect the fibre and shape how it feels and reflects light.
- Cortex — the bulk of the strand, where most of its strength and elasticity live.
- Medulla — a central core that is present in some fibres and absent in others.
The growth cycle
Each follicle cycles independently, which is why hair doesn't all shed at once.
| Phase | What's happening | Rough duration |
|---|---|---|
| Anagen | Active growth; the fibre is being produced | Years |
| Catagen | A short transition; growth stops | Weeks |
| Telogen | Resting, then release of the fibre | Months |
Durations vary between people and between follicles on the same head.
Shedding vs breakage
A shed hair completes its cycle and releases from the follicle — it often has a small pale bulb at the root end.
A broken hair snaps somewhere along the fibre. Both ends look like hair, and lengths are usually uneven.
The distinction matters because shedding is follicular and breakage is a fibre-care question. Persistent or significant shedding, thinning or scalp symptoms may warrant evaluation by a qualified healthcare professional.
Growing hair and keeping hair are different projects
Follicular growth rate is largely outside cosmetic control. What products and habits can influence is how much of that growth you keep.
If length seems stuck, the more useful question is usually not "how do I grow faster" but "where am I losing length".
How Hairavie knows this
Hairavie cites peer-reviewed research, scientific reviews, reference textbooks, dermatology organisations and government health resources. Beauty blogs are never used as scientific authority.
- Scientific reviewBuffoli, B. et al. (2014). The human hair: from anatomy to physiology. International Journal of Dermatology
- Reference textbookRobbins, C. R. (2012). Chemical and Physical Behavior of Human Hair (5th ed.). Springer
- Dermatology organisationHair care and hair loss guidance for the public. American Academy of Dermatology. View source
Keep reading
Understanding Your Hair Pattern
Pattern describes the shape your hair takes. It is a useful description, not a complete profile of how your hair behaves.
5 min readFine, Medium & Coarse Strands
Strand thickness is the width of a single fibre. It is not the same as how much hair you have.
5 min readHair Density Explained
Density counts fibres per area of scalp. It shapes volume and product quantity — not fibre behaviour.
4 min readHairavie provides cosmetic hair-care education only. It does not diagnose or treat medical or scalp conditions. If symptoms persist or you're concerned about hair loss or scalp health, consult a qualified healthcare professional.