Damaged human hair, coloured scanning electron micrograph (SEM). Human hair is made up of a strong fibrous structural protein called keratin. In normal, healthy hair the outer layer (cuticle) has overlapping scales of keratin that run smoothly along the length of the hair. The hair in this image has been continuously exposed to vivid, bright, unnatural colouring with strong bleaching agents as well as daily heat treatment in the form of straightening tongs. This has resulted in the keratin scales being no longer visible. The scales appear to have been completely broken down and destroyed with the cuticle displaying extreme damage. Magnification: x130 when printed at 10cm wide