Understanding Reality, written by Chang Po-tuan in the tenth century, is concerned with the principles of inner alchemy. The Inner Teachings of Taoism, another of Chang Po-tuan’s classics on inner alchemy, uses colourful metaphorical language to summarise the essentials of self-transformation. The Book of Balance and Harmony is a classic Taoist anthology of essays, conversations, poetry and songs, and Practical Taoism is a collection of the most accessible texts on inner alchemy.