Cultured pearls are pearls that are created through human intervention. They are formed when a small irritant, such as a bead or piece of shell, is inserted into an oyster or mollusk. The creature then secretes layers of nacre, a substance that forms the pearl, over time. This process can take several months to years, depending on the type of pearl and the conditions in which it is grown. The most common types of cultured pearls are Akoya, Freshwater, South Sea, and Tahitian pearls. Each type varies in size, shape, and color, influenced by the species of mollusk and the environment. Cultured pearls are valued for their beauty and luster, making them popular in jewelry.