The visible shafts of hair and nail plates are mostly keratinised, non-living cells. Growth happens in living tissues: hair follicles in skin and the nail matrix under the skin at the nail base.
Hair grows in cycles
Each follicle passes through growth, transition and resting phases. Because neighbouring follicles are not synchronised, everyday shedding does not usually make all hair disappear at once.
Hair colour depends largely on melanin made near the growing root. Greying occurs as pigment production falls, influenced strongly by genes and age.
Nails grow from a hidden factory
New nail cells form in the matrix and push older compacted cells forward. Fingernails generally grow faster than toenails, but growth varies with age, health, season and injury.
Cutting hair or nails is painless when only the non-living part is trimmed. Cutting into skin or the nail bed hurts because living tissues contain nerves and blood vessels.
Measure growth without marking the body
- Photograph one clean fingernail beside a ruler with permission.
- Repeat weekly from the same angle.
- Measure the movement of a natural ridge or the free edge.