Alchemy covers several philosophical traditions spanning some four millennia and three continents. These traditions' general penchant for cryptic and symbolic language makes it hard to trace their mutual influences and "genetic" relationships. One can distinguish at least three major strands, which appear to be largely independent, at least in their earlier stages: Chinese alchemy, centered in China and its zone of cultural influence; Indian alchemy, centered on the Indian subcontinent; and Western alchemy, which occurred around the Mediterranean and whose center has shifted over the millennia from Greco-Roman Egypt, to the Islamic world, and finally medieval Europe. Chinese alchemy was closely connected to Taoism and Indian alchemy with the Dharmic faiths, whereas Western alchemy developed its own philosophical system that was largely independent of, but influenced by, various Western religions. It is still an open question whether these three strands share a common origin, or to what extent they influenced each other.