Mollusks are found in almost every habitat on Earth. It is estimated that there are between 50,000 and 200,000 species of mollusks, most living in marine environments.

Mollusks occur in all shapes, sizes, and even colors. The largest mollusk is the Collosal Squid, which can reach over 40 feet (13 meters) in length and weigh over 1,000 pounds (494 kg). Some adult mollusks measure as small as 1.5 milimeters.