All teas originate from the same species, the Camelia Sinensis. To make green tea, the fresh tea is briefly cooked using either steam or dry heat. This process fixes the green colors and fresh flavors. Black tea leaves are left outside and become limp (withered), then put into machines that roll the leaves and damage them. The damaged leaves change color to brown, then black. This natural process is called oxidation and is similar to the ripening of a banana (from yellow to brown and finally becoming black.) After all the tea is dried, it can be shipped great distances. The oxidation process changes the flavor of the tea (now black) and gives it more body.