Green tea is made from Camellia sinensis leaves that have not undergone the same withering and oxidation applied when processing Camellia sinensis into oolong tea and black tea. Green tea originated in China, but its production has spread to many countries in Asia. Tea consumption has its legendary origins in China dating back to more than 4,000 years ago, making it the oldest plant-based tea known. According to legend, green tea was first brewed in 2737 BC during the reign of Emperor Shennong.