False-colour scanning electron micrograph of Gore- Tex, a fabric used to make waterproof clothing. The fabric resembles a sandwich with nylon forming the outer layers and teflon the filling. Here, the nylon is the pink layers top and bottom. The teflon is a microporous membrane (yellow/white) made up of a web of nodules connected by fine fibrils. The pores in the web are less than a micrometre in diameter, 20,000 times smaller than a drop of water but 700 times larger than a water molecule. Consequently garments made from Gore-Tex are waterproof while allowing perspiration from the body to pass through. Magnification: x100 at 6x4.5cm size.