Mold(s) reproduce by means of spores, or seeds. These spores will often settle on damp surfaces and begin to swell to 2-3 times their original size. A they do so, they begin to form thread like structures called Hyphae. As the Hyphae grow larger, they begin to interweave and form a mass called a Mycelium. This is the point where we notice mold with the naked eye. This cycle continues as the fungus matures and spores are carried away.
One of the key ingredients in mold growth is moisture. Mold(s) need moisture and nutrients to thrive. This is why we often find mold in places where water is present. Bathrooms, kitchens, basements and attics are some of the common culprits. However, even places or materials that seem or feel dry can hold moisture and start mold growth.