Yeasts are unicellular fungi and so far over 1 500 different species have been described. Among them are important industrial organisms, pathogens and model organisms which help us to understand how eukaryotic cells work.However, one of the most well-known characteristics of yeast is the ability of Saccharomyces cerevisiae, baker’s yeast, to ferment sugar to 2-carbon components, in particular ethanol, without completely oxidising it to carbon dioxide, even in the presence of oxygen, as many other microbes do. This fermentative ability is essential for the production of wine, beer and many other alcoholic beverages.