Moulds are a species of fungus found almost everywhere in natural environments, namely in the ground, on plants and on withered vegetation. Moulds decompose plants and other organic material, and as such play a vital role in the cycle of nature.
Indoors, however, moulds are very undesirable. They grow through a network of microscopic threads called hypha and disperse via airborne spores.
Moulds thrive in damp, warm surroundings, but the spores can survive desiccation and re-sprout should these surroundings become humid again.
Moulds appear in a variety of shades: white, grey, yellow, red, green, brown and black.