These tiny oranges, known as clementines in the United States, are typically hollowed out and filled with tea, then aged. I have several that were obtained in Guandong, China, in 2005 and have since been aged in man-made pu-erh caves in the United States. The leaves, when steeped, have a zesty orange smell; the tea is smooth and malty, with hints of orange, especially if you use part of the rind while steeping. I was surprised that the orange notes were not more pronounced, but overall these make for a very interesting conversation piece and a very tasty tea.
Here are some reviews of this pu-erh: