炼丹, or "alchemy," is an ancient practice that originated in China, focusing on the transformation of materials to achieve immortality and spiritual enlightenment. Practitioners, known as alchemists, sought to create the mythical substance called 长生不老药 (elixir of life), believed to grant eternal life. The process of 炼丹 involved various techniques, including heating, mixing, and refining natural substances like metals and herbs. Alchemy played a significant role in the development of early chemistry and medicine, influencing later scientific discoveries and practices in both 中国 and the broader world.