In modern times, Alchemy is often dismissed as merely a confused form of proto-chemistry, obsessed with turning lead into gold. The reality of the European Alchemical tradition is much more profound and complex.
European Alchemy of the 15th through the 18th centuries was something of a catch-all of mysticism, philosophy, natural science, medicine, astrology, and astronomy.
It drew heavily on the Hermitic writings of the early Christian era (which, in turn, traced their origins back to Pharonic Egypt) as well as Greek and Roman neo-Platonism. But European Alchemy was most profoundly influenced by the alchemical traditions in Sufism and Islamic philosophy, which itself was influenced by the ancient Mediterranean traditions, as well as alchemical traditions of Indian Yoga and possibly even Chinese Taoism.
At its heart, Alchemy is focused on transformation. Yes, there was certainly a strong tradition of "practical Alchemy" that was concerned with lab work, the creation of tinctures and the transmutation of materials, including changing lead into gold. These schools of Alchemy were often more broadly interested in communing with the elements of the natural world, the development of medicines and the discovery or re-discovery of herbal remedies for the relief of suffering and the pursuit of long life. In this way, it was a mystically infused form of physical Alchemy, similar to many practices in China and India.
But there has always been a broad awareness in Alchemy that tended to view the lab work as a metaphor for the subtle body and, more purely, the spirit. The plants and the minerals and natural forces refered to so often in Alchemical writings and drawings correspond to regions of the energetic body.
As a commonly used example, "lead" corresponds to the energy center of the seat (the muladhara or first chakra, in Yogic terminology), while "gold" is the crown (the sahasrara or seventh chakra). Understood this way, the transmutation of lead into gold, is the raising of the vital (Kundalini) energy from the seat to the crown. The perfect wholeness that is then experienced, often amidst a radiant white light, is the white stone of the philosopher -- the ultimate goal of Alchemy.