Used in China for more than 2,500 years, soy sauce is one of the world's oldest condiments, made by fermenting a combination of salt, enzymes, and mashed soybeans. It originates from ancient China between the 3rd and 5th century, when preserved foods were commonly known as jiang, a predecessor to what we know today as soy sauce.
Since jiang made from soybeans and wheat was the most accessible, it developed quite rapidly, spreading from China to Japan and other neighbouring regions and countries. Before today's mass production, the preparation of soy sauce was a laborious process, resulting in a brew with a delicately meaty, earthy flavor.
The producers who still ferment the ingredients in an old-fashioned way claim it takes from six months to a year (or even longer) to produce this delicious condiment, giving it umami, the so-called fifth flavor. As a rule of thumb, the darker the soy sauce, the more desirable it is.