Natural wine is more of a concept than a well-defined category with agreed-upon characteristics. In its purest form, it is wine made from unadulterated fermented grape juice and nothing else. In a more relaxed meaning of the term, natural wines are achieved under the guiding principle of minimum human intervention (e.g., without the addition of cultured yeast or any treatments such as acidification or clarification, among others. Orange wines, for which not even the skins are extracted before fermenting white grape varieties, stand as the prototype example of a natural wine.