Coloured scanning electron micrograph (SEM) of hair cells from the organ of Corti in the cochlear of the inner ear of a guinea pig. Each V-shaped arrangement of outer hairs (stereocilia, white) lies on the top of a single cell. The hairs are surrounded by endolymph fluid. As sound enters the ear, it causes waves to form in the endolymph, which in turn causes these hairs to move. Outer hair cells amplify the vibrations, which are then picked up by inner hair cells (not seen) that transmit the signal to auditory nerve fibres. This amplification enhances the sensitivity and dynamic range of hearing. Magnification: x7,000 when printed at 15cm wide.