Green tea is a type of tea that is made from Camellia sinensis leaves and buds that have not undergone the same withering and oxidation process used to make oolong teas and black teas. Green tea originated in China, but its production and manufacture has spread to other countries in East Asia. Several varieties of green tea exist, which differ substantially based on the variety of C. sinensis used, growing conditions, horticultural methods, production processing, and time of harvest. Although there has been considerable research on the possible health effects of consuming green tea regularly, there is little evidence that drinking green tea has any effects on health.