STR/00 The Section

Four layers, one diagram.

Focus any layer below and the diagram finds it. This is the same live diagram used across the site -- rendered here at full height, with the science behind each band written out in full.

Stratum Corneum

15-20 µm

Dead, flattened corneocytes bound in a lipid matrix. This is the layer most leave-on skincare is formulated to interact with directly.

Facial skin, typical range -- thickness varies roughly 100x across the body (eyelid to sole).

Viable Epidermis

50-100 µm

Living keratinocytes, melanocytes and Langerhans cells. Renews roughly every 4-6 weeks in healthy adult skin.

Below the corneum; thinner over the eyelids, thicker on the palms and soles.

Dermis

1.0-3.0 mm

Collagen and elastin fibres, blood vessels, nerve endings and fibroblasts -- the cells that synthesise new collagen.

Facial skin; the back and scalp run considerably thicker.

Hypodermis

3.0-30.0 mm

Subcutaneous fat and connective tissue. Insulation, cushioning, and an energy reserve.

Thickness varies enormously by body site and individual; shown here only to complete the section.

Surface Hypodermis

STR/00b How This Is Drawn

The diagram is rendered live in your browser, not pre-drawn -- but it is a readable proportion, not a literal one.

Real facial-skin depth spans roughly 15 micrometres of corneum to several centimetres of hypodermis -- over a thousand-fold range. Drawn at true linear scale, the corneum would be a single invisible pixel and the diagram would be useless as a reference. So the four bands here keep their real relative order and their real relative proportions to one another within a readable range, and every place this diagram appears is captioned as illustrative rather than measured.

Each band is textured differently on purpose: the corneum is drawn as tight tessellated cells, the epidermis as rounder keratinocyte-like clusters, the dermis as flowing fibre streaks standing in for collagen and elastin, and the hypodermis as sparse, larger rounded forms standing in for fat cells. None of this is a microscopy image -- it is a diagram, and we would rather it read honestly as one than dress it up as something it is not.

See which formulas are built around each layer, or read the full ingredient index.