Petticoats are a type of undergarment worn beneath skirts or dresses, primarily designed to add volume and shape. Traditionally made from cotton, silk, or lace, they can be layered to create a fuller silhouette. Petticoats were especially popular in the 19th century and are often associated with styles like the Victorian and Edwardian eras. In modern fashion, petticoats are less common but still used in certain styles, such as ball gowns or retro dresses. They can also serve practical purposes, providing warmth or modesty. Today, petticoats are often seen in vintage clothing or as part of themed costumes.