From the human perspective, a pearl is a beautiful and valuable treasure. From the perspective of Nature, a pearl is a mistake that needs to be neutralised and hidden. Pearls forms as the immune response of a shelled mollusc to a foreign body. Many of us admiring the beauty of pearls tend to believe that this organic gem forms because of a sand grain intrusion into a shell. However, the reality is much more brutal: natural pearls form from intrusion of parasites or other foreign bodies during the breathing or nurturing of a mollusc. If this happens, a mollusc starts isolation of a foreign substance by coating it with layers of calcium carbonate and other materials, usually shaping it into a glittering round form. In the factories of artificial pearls, the process is considerably simpler: a round formation is seated into a shelled mollusc and the mollusc coats the upper layers of the formation.