Tea is an aromatic beverage commonly prepared by pouring hot or boiling water over cured leaves of the Camellia sinensis, an evergreen shrub (bush) native to East Asia. After water, it is the most widely consumed drink in the world. There are many different types of tea; some, like Darjeeling and Chinese greens, have a cooling, slightly bitter, and astringent flavour, while others have vastly different profiles that include sweet, nutty, floral or grassy notes. Tea has a stimulating effect in humans primarily due to its caffeine content. Tea originated in Southwest China during the Shang dynasty, where it was used as a medicinal drink. An early credible record of tea drinking dates to the 3rd century AD, in a medical text written by Hua Tuo. It was popularised as a recreational drink during the Chinese Tang dynasty, and tea drinking spread to other East Asian countries. Portuguese priests and merchants introduced it to Europe during the 16th century. called tisanes or herbal infusions to prevent confusion with tea made from the tea plant.