The Longan fruit comes from a tree that is found in South and Southeast Asia.
From Wikipedia: “The longan (龍眼)—translated literally as “dragon eye”—is so named because it resembles an eyeball when its fruit is shelled (the black seed shows through the translucent flesh like a pupil/iris). The seed is small, round and hard, and of an enamel-like, lacquered black. The fully ripened, freshly harvested shell is bark-like, thin, and firm, making the fruit easy to shell by squeezing the fruit out as if one is “cracking” a sunflower seed. When the shell has more moisture content and is more tender, the fruit becomes less convenient to shell. The tenderness of the shell varies due to either premature harvest, variety, weather conditions, or transport/storage conditions.
The fruit is edible, extremely sweet, juicy and succulent in superior agricultural varieties, and apart from being eaten fresh, is also often used in East Asian soups, snacks, desserts, and sweet-and-sour foods, either fresh or dried, sometimes canned with syrup in supermarkets.
Dried longan, called guìyuán (桂圆) in Chinese, are often used in Chinese cuisine and Chinese sweet dessert soups. In Chinese food therapy and herbal medicine, it is believed to have an effect on relaxation. In contrast with the fresh fruit, which is juicy and white, the flesh of dried longans is dark brown to almost black. In Chinese medicine the longan, much like the lychee, is thought to give internal “heat” (上火).”
Longan fruit are said to have anti-cancer, antioxidant, and liver-protective properties. The longan contains high levels of iron, potassium, and large amounts of vitamins A and C.