You have probably seen mold growing on long-forgotten food in the fridge or in the great outdoors. Mold is a fungus, just like mushrooms and yeasts. It is reproduced through spores, which spread on currents of air. What causes mold growth? There are up to 300,000 types of mold in the world, and each requires specific scenarios to thrive. However, most molds grow best in warm, damp areas with inadequate ventilation. Molds also need nutrients such as cellulose such as plant material including wood and cardboard, fabrics or even dead skin cells.