Fungi are legit the fun guys! unless they cause diseases. Fungi are a diverse group of eukaryotic organisms, almost omnipresent.
There was bread in the house which I had forgotten existed for 3 days straight! and voila what I get to see is the assorted fungus which grew in those 3 days! That too, in different colors like- black, mint green, yellow, beige. Fungal spores are present in the air, and as soon as they get their preferred substrate or food, they flourish and thrive out there.