Short answers, pulled from the story.
Alchemy is an ancient branch of natural philosophy and a protoscientific tradition practiced in China, India, the Muslim world, and Europe across approximately four millennia. Its Western form is first attested in pseudepigraphical texts from Greco-Roman Egypt during the first few centuries AD, where Alexandria was the central hub of alchemical knowledge.
Alchemists sought chrysopoeia (the transmutation of base metals such as lead into gold), the creation of an elixir of immortality, and panaceas capable of curing any disease. The perfection of the human body and soul was also considered an aim, all of which were connected to the concept of the philosopher's stone and the Great Work, or magnum opus.
Mary the Jewess, dated to around 200 AD, is the first alchemist whose name is recorded. She is credited with inventing or improving the bain-marie water-bath, the tribikos distillation apparatus, and the kerotakis. Her work is known through the early-4th-century writings of Zosimos of Panopolis, as none of her own writing has survived.
After the fall of the Roman Empire, the Islamic world became the center of alchemical development and preserved most earlier texts as Arabic translations. Jabir ibn Hayyan, working in the late 9th and early 10th centuries, introduced methodical classification of substances and clear descriptions of laboratory processes, and his work originated the atomic theory of corpuscularianism and introduced the philosopher's stone to Western alchemy.
Alchemy entered Latin Europe on the 11th of February 1144, when Robert of Chester completed his translation of the Liber de compositione alchemiae from Arabic. Robert noted in his preface that alchemy was unknown in Latin Europe at the time of his writing. The translation movement that followed was centered largely in 12th-century Toledo, Spain.
Carl Gustav Jung revived and popularized alchemical symbolism in analytical psychology after receiving a copy of The Secret of the Golden Flower, a Chinese alchemical text. He identified a direct parallel between alchemical imagery and the inner images arising in his patients' dreams and visions, interpreting the alchemical quest as a map of psychological transformation he called individuation. His magnum opus on the subject is volume 14 of his Collected Works, Mysterium Coniunctionis.