Century eggs (Chinese: 皮蛋; pinyin: pídàn; Jyutping: pei4 daan2), also known as preserved eggs, hundred-year eggs, thousand-year eggs, thousand-year-old eggs, millennium eggs, skin eggs, or black eggs, are a Chinese egg-based culinary dish made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, quicklime, and rice hulls for several weeks to several months, depending on the method of processing.