Outer alchemy,
外丹, cooked cinnabar, lead and sulphur into pills meant to make the eater immortal; many contained mercury. From the Tang and Song on,
金丹 more often meant inner alchemy,
内丹, the refining of one's own essence, breath and spirit. Xianxia novels turned this into a ladder of realms:
炼气,
筑基,
金丹,
元婴.
