Inner ear hair cells. Coloured scanning electron micrograph (SEM) of hair cells in the organ of Corti. This delicate structure in the cochlea of the inner ear converts sound vibrations into nerve impulses. Each of the outer hair cells in the three rows at top have V-shaped groups of stereocilia, while each inner hair cell (bottom) has a single row of stereocilia. These cells are surrounded by a fluid called the endolymph. As sound enters the ear it causes waves to form in the endolymph, which in turn cause these hairs to move. The movement is converted into nerve impulses that are passed to the brain. Magnification: x4000 when printed 10cm wide.