Stevia is a natural sweetner discovered by Moisés Bertoni in my hometown (Foz do Iguaçu, Brazil) right on the borders with Paraguay.
Locally it is also known by the name "ka'a he'ê" (pronounces Ka-a Hey-E) in Tupi-Guarani.
The industrialized ka'a he'ê tastes horrible if compared to the real thing.
In my hometown region, it's normal to have ka'a he'ê as an ornamental plant in most houses. Even more normal is somebody serve tea or coffee and instead of sugar pots, there's a small vase with a young ka'a he'ê plant. each leaf is equivalent to 1 teaspoon of sugar and it tastes sweet exactly like sugar You just stir the leaf in the cup for a few seconds.
What can be more natural that simply pull a couple of leaves from a plant and stir it in your hot drink?
Strangely, the after taste is also impressive. Even if you put several leaves, to toss a whole plant in the cup, the drink will be super sweet but you won't have that nasty and nauseating taste of excess sugar.
Now, the industrialized powder crap and the sodas made with ka'a he'ê are terrible. I don't know if my taste is too sensitive of if i'm too used to the real thing straight from the plant but I can taste a horrible chemical after taste, just like any other artificial sweetner.