Fungi (“fungus”, pl. “fungi”, from the Greek word “σπόγγος”, “σφόγγος”) is a distinct class of organisms and is taxonomically classified into a separate kingdom, which is the second most populous (after insects) group of organisms in the biosphere. The number of fungi recorded species globally is about 100.000, while there is a conservative estimation that the total size of existing species exceeds 1.5 million. Well-known fungal species are only 7% of the total estimated population, so the vast majority of them are unknown, although their significance for nature and human is enormous. Of the 100.000 fungal species, about 20.000 are classified as macromycetes (fungi with characteristic macroscopically visible fruitbodies – mushrooms), of which about 2.000 form edible mushrooms, but only a few dozen of them are grown on a commercial scale for human consumption. More than 4.000 fungal species have been recorded in Greece, of which around 3.000 correspond to macromycetes.