Fruit fly (Drosophila melanogaster), coloured scanning electron micrograph (SEM). The fruit fly is considered a model organism as it is widely studied, able to reproduce rapidly, easy to maintain in a laboratory and has a genetic system that is well understood. The fruit fly has been used for over a century to study a range of biological processes including genetics, embryonic development, physiology and pathology. Many biological mechanisms and pathways that control development are conserved across evolution between humans and fruit flies with about 75% of human disease genes having a recognizable counterpart in the genome of the fruit fly. Magnification: x400 when printed at 10cm wide