Fingerprint. Coloured scanning electron micrograph (SEM) of part of a human fingerprint from a male index finger, showing details of skin ridges in the outer cornified (keratinised) epidermis. These minute ridges form a distinct pattern, with each fingerprint pattern unique to an individual. Even identical twins have different fingerprints. The patterns are classified into four main types: loops, whorls, arches, and combinations of these three. Magnification: x5 at 6x4.5cm size.