Century egg (Chinese: Pidan); also known as thousand-year-old egg, preserved egg, and hundred-year egg, is a Chinese delicacy made from eggs, usually from that of a duck or chicken.
Century eggs are made by putting eggs into a mix of cement, ash, and lime, and letting the mixture preserve the eggs for a number of weeks or months. The preserved eggs have a brown shell with snowflake-like patterns, a rich brown egg white, and a bright green yolk. The taste of century eggs has been compared to strong cheese.