When presenting examples of particularly species-rich ecosystems, we will most probably name tropical coral reefs, tropical gallery forests or selected types of tropical rainforests. To visit these ecosystems, one must travel a long journey far outside of homeland, and even beyond borders of our continent. Still, a comparably species-rich ecosystem can be found, even in our conditions – yet escaping broader awareness when speaking about biodiversity. This is perhaps caused by simple fact, that thousands of species inhabiting this ecosystem could only rarely be observed by the naked eye, as they are mostly of the microscopic size. Indeed, healthy, and well-functioning soil – in our conditions mostly soil of broad-leaved deciduous or mixed forests – is a real biodiversity hotspot reachable just “beyond our courtyards” or next door. Presence of the particular species, overall species richness and relative numbers of soil organisms serves at the same time as great indicator of soil conditions, and often also of the quality of respective above-ground ecosystem at the place.