Collagen fibres. Coloured scanning electron micrograph (SEM) of collagen from the dermis of the skin. Collagen is a protein with a high tensile strength, providing structure and elasticity to skin, tendons, ligaments and bones. It is the most abundant protein in the body. In the dermis, collagen forms rope-like fibres that are arranged irregularly. Magnification: x1300 when printed 10 centimetres wide.