Oolongs are considered by most to be the most difficult to produce and the most interesting to taste. Unlike Green teas, which are not allowed to oxidize at all, and Black teas, which are 100% oxidized, oolongs are partially ozidized falling somewhere in between. Where they fall in between depends upon the tea, they can be very green (see the Ti Kuan Yin) to almost black (Shui Hsien Oolong)
Taiwan, still referred to as Formosa in the tea world, is considered by many to be the champion of Oolongs. Prized Tiawanese Oolongs will often be drank in ceremonious style where the tea is brewed for many infusions for very short times. 30 seconds to 1 minute per infusion for up to 20 infusions depending upon the tea! The Taiwanese treasure their tea and with good reason (Tung Ting Oolong).