"Aspergillus fumigatus", a saprotroph widespread in nature, is typically found in soil and decaying organic matter, such as compost heaps, where it plays an essential role in carbon and nitrogen recycling. Colonies of the fungus produce from conidiophores; thousands of minute grey-green conidia (2–3 μm) which readily become airborne. For many years, "A. fumigatus" was thought to only reproduce asexually, as neither mating nor meiosis had ever been observed. In 2008, "A. fumigatus" was shown to possess a fully functional sexual reproductive cycle, 145 years after its original description by Fresenius. Although "A. fumigatus" occurs in areas with widely different climates and environments, it displays low genetic variation and a lack of population genetic differentiation on a global scale. Thus, the capability for sex is maintained, though little genetic variation is produced.