They are everywhere - and have been since time immemorial: in the air, in the water and on the land. From the very beginning they have been part and parcel of life. Yet many aspects of these organisms remain inexplicable, even to modern science. Despite their obvious multiplicity, we classify them all in one collective term: fungi. Some 100,000 species have been identified to date worldwide. But the actual number will probably be far higher, because virtually every expedition to tropical countries brings new species to light. Some fungus specialists estimate that there might be around 1.5 million species of fungus on our planet.