Twinings oolong tea, like other oolong teas, is a semi-oxidized tea made from the same species of tea leaf as green and black teas: Camellia sinensis. Green tea is made from unoxidized tea leaves, whereas black tea comes from fully oxidized tea leaves. The leaves of oolong tea are left only until oxidization sets in on the outer edges of the leaves. Several studies have indicated potential benefits of oolong tea.