Within these main categories of tea are vast varieties of individual beverages. Some researchers have counted more than 700 of these beverages. Others put the number at more than 1,000. Some of the variations are due to different strains of the Camillia plant. The Tieguanyin, for example, is traced back to a single plant discovered in Anxi in Fujian province. Other teas draw some of their characteristics from local growing conditions. However, the largest factor in the wide variations comes from differences in tea processing after the tea leaves are harvested. White and green teas are heat-treated () soon after picking to prevent oxidization, often called fermentation, caused by natural enzymes in the leaves. Oolong teas are partially oxidized. Black teas are fully oxidized. Other differences come from variations in the processing steps.