Wound dressing. Coloured scanning electron micrograph (SEM) of a varihesive wound dressing. The outer layer (blue) consists of polyurethane (PU) foam and is water and germ-proof, but allows the wound to breathe. The inner matrix consists of the polymers carboxymethylcellulose, pectin and gelatine which are able to absorb any exudate from the wound. This creates an environment around the wound that hastens the healing time and minimises scars. Magnification: x830 when printed at 10 centimetres wide.