How does the skin work?

Your skin is your largest organ: about 2 square metres that keeps water in, germs out and your core at 37 °C. Cut open a block of it, follow a cell from birth to flake, sweat through a humid heatwave, feel with five kinds of sensor, and see why skin comes in every shade.

Read how it works: How does the skin work? · The history of understanding the skin · More boxes on Glassbox

Chapters in this interactive model

1. The body’s largest organ: Three layers, about 2 m² and 4 kg, packed with hair, glands, nerves and blood.
2. A wall that rebuilds itself: New cells rise, flatten and die into bricks and mortar, then flake away, about every 4 weeks.
3. Your built-in air conditioner: Sweat, blood flow and goosebumps hold your core near 37 °C, until the air is too hot and humid.
4. Five kinds of touch sensor: Pressure, flutter, vibration, stretch and pain, each felt by its own receptor.
5. Melanin, the skin’s own sunshade: Why skin comes in every shade, how UV burns and tans, and what SPF really means.
6. How skin heals, and what goes wrong: Cuts, scars, burns, acne, eczema and moles: general facts, not medical advice.