Did you know, that your body contains a larger number of bacteria than human cells. The world inside and around us is dominated by "good" bacteria we rely upon. Not only this is fascinating and worth some reading, bacteria and yeast also produce my new favorite drink - Kombucha. Here's an introduction to the topic derived from the ultimate book about fermentation from Sandor Katz.
Kombucha is sugar-sweetened tea fermented by a community of organisms into a delicious sour tonic beverage, sometimes compared to sparkling apple cider. Kombucha is typically produced by a SCOBY, also known as a mother, that takes the form of a rubbery disk, which floats on the surface of the tea as it ferments. The community of organisms can also be transferred via the kombucha liquid itself, which can generate a new SCOBY. The Kombucha mother closely resembles a vinegar-making by-product, mother-of-vinegar, and is composed of many of the same organisms; indeed, some analysts have come to the conclusion that they are exactly the same.
No other ferment even approaches Kombucha in terms of its sudden dramatic popularity (at least in the United States). Kombucha has enjoyed acclaim in many varied locales, widely promoted as beneficial to health, notably in Central and Eastern Europe over the course of the last century, and its use has been growing in the United States since at least the mid-1990s. Today there are dozens of commercial enterprises manufacturing and selling Kombucha—ranging from small start-ups to multinational corporations.
Like any ferment, it contains unique metabolic by-products and living bacterial cultures that may or may not agree with you. Try some, starting with small servings, and see how it tastes and feels to you. Many enthusiasts regard Kombucha as something of a miracle cure-all.
Source: Katz, The Art of Fermentation, 2012