Coloured scanning electron micrograph (SEM) showing the inner ear hair cells (pale pink) found in the Organ of Corti in the cochlea of the inner ear. These hairs are surrounded by a fluid called the endolymph. When sound enters the ear, it causes waves to form in the endolymph, which in turn makes the hairs move. The movement is converted into an electrical signal, which is then sent to the brain.