The rhabdom is a transparent, rod-like structure that is located in the center of each ommatidium, a visual unit in the compound eyes of arthropods. It is made up of microvilli, which are finger-like processes contributed by a small number of photoreceptor cells.
Light is focused onto the rhabdom by the facet lens and crystalline cone of the ommatidium. The rhabdom is connected to a set of neuronal relays by a single axon.
