Molds are types of fungi. They grow in the natural environment. Tiny particles of molds are found everywhere in indoor and outdoor air. In nature, molds help break down dead materials, and can be found growing on soil, foods, plants and other items. Molds are also very common in buildings and homes. Mold needs moisture to grow. Indoors, mold growth can be found where humidity levels are high, like basements and showers. Molds produce microscopic cells called "spores" that are spread easily through the air. Spores can also be spread by water and insects. Live spores act like seeds, forming new mold colonies when they find the right conditions.