Drosophila melanogaster is a commonly used model organism in biological sciences.
It is frequently used in neuroscience and behaviour sciences due to its well characterised behaviour. These behaviours can be disrupted by certain mutations, such as to genes essential to the circadian clock and courtship. The fly eye is heavily studied as a model for vertebrate vision. Flies have one of the most advanced visual systems amongst insects. The eyes are structured into hexagonal tessellating units called ommatidia, which each contain eight photoreceptor cells.