Stevia (aka Sweet leaf, Sugarleaf) is a 100% natural sweetener made from the herb Stevia rebaudiana Bertoni. Originally from Paraguay, now grown in Japan, Korea, China (80% of Worldwide production grown in China), and Brazil and other parts of South America. Widely used in Asia and South America for over 200 years. Still most often considered a herb or dietary supplement, stevia is available in most health food stores, but it has even begun to surface in mainstream products after its approval for use as an additive by the FDA in 2008.
Stevia has zero calories, does not affect blood sugar, therefore is low glycemic, is 200-400 times sweeter than sugar when refined, and is stable at high temperature (for cooking/baking).
Stevia, like most sweeteners, is available in both powdered and liquid varieties, so your usage will vary depending on which variety you select. Both varieties are incredibly sweet; you’ll only need about one quarter of the amount that you would use if you were using sugar. Some people complain about stevia’s bitter after taste but high purity stevia is not bitter and has no lingering aftertaste.
More information: http://en.wikipedia.org/wiki/Stevia