In the image above you can observe a mosquito eye. Like all other insects, the mosquito has compound eyes – spheres comprising hundreds or thousands of units called ommatidia (ommatidum sg. from the greek ommatidis – small eyes). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part of the ommatidium is overlaid with a transparent cornea. Each ommatidium is innervated by one axon and thus provides the brain with one picture element. The brain forms an image from these independent picture elements.