A pearl is a smooth, round gem that forms inside certain oysters and other shellfish. Unlike diamonds or rubies that miners dig from the earth, pearls grow inside living creatures. When something gets stuck inside an oyster's shell, the oyster protects itself by coating it with layers of a smooth, shiny substance called nacre. Over several years, these layers build up into a pearl.

Natural pearls are rare and valuable, which is why people have prized them for thousands of years. Today, most pearls come from pearl farms, where people carefully place a small irritant inside oysters to start the process. These cultured pearls are still real pearls, just grown with human help.

Pearls come in different colors: white, black, pink, or golden, depending on the type of oyster and where it lives. The most valued pearls are perfectly round and have a lustrous glow, though baroque pearls with unusual shapes have their own beauty.

People use pearl to describe anything precious and rare. A grandmother might call her grandchild “my little pearl.” In literature, something described as a pearl of wisdom is an especially valuable piece of advice.