A petticoat is a type of undergarment worn beneath a dress or skirt. Traditionally, it is made of lightweight fabric and can be ruffled or layered to add volume and shape to the outer garment. Petticoats were especially popular in the 19th and early 20th centuries, often worn to create a fuller silhouette. In addition to providing shape, petticoats can also serve practical purposes, such as providing warmth or modesty. They are often associated with historical fashion and are sometimes seen in period costumes or vintage clothing, reflecting styles from eras like the Victorian period or the Roaring Twenties.