A single teaspoon of healthy soil contains more microorganisms than there are people on Earth.
Why it is true
These microorganisms include bacteria, fungi, and protozoa that play crucial roles in decomposing organic matter and recycling nutrients, sustaining all plant life.
Source: Microbiology
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.