Your Largest Organ

Skin is your largest organ. Stretched flat, it would cover roughly 2 square meters — about the size of a shower curtain — and it can account for around a seventh of your body weight.

It is also one of the few organs you can watch work. The surface you see is mostly dead cells, constantly flaking off and being pushed up from below. Your whole outer layer renews itself roughly every few weeks, so the skin you have now is not the skin you had last month.

Those flaking cells are not waste. As skin cells rise to the surface, they flatten, fill with a tough protein, and die on purpose. The result is the stratum corneum — a layer built like a brick wall, with dead cells as the bricks and a fatty seal as the mortar.

This layer of dead cells is your front line. It keeps water locked inside your body and keeps bacteria, chemicals, and UV locked out. A barrier made of dead cells is doing some of the most important living work you have.