The history of tea is long and complex, spreading across multiple cultures over the span of thousands of years. Tea likely originated in southwest China during the Shang dynasty 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. Tea was first introduced to Portuguese priests and merchants in China during the 16th century. Drinking tea became popular in Britain during the 17th century.