Wine is produced from a microbiological phenomenon: yeasts of the Saccharomyces cerevisiae species develop in the absence of air and break down the grape sugars into alcohol and carbon dioxide; this is the alcoholic fermentation. During this process, many secondary products appear ( glycerol, succinic acid, esters, etc...), which help from the wine's aroma and taste. The yeasts find all the chemical constituents in the grape mash ( carbon, nitrogen, mineral elements, vitamins etc...) necessary for their life. In any case, the quality and characteristics of the wine depend essentially on the quality of the grape, therefore on natural factors ( varietals, vineyards, terroirs)