Yeast is naturally present on the skins of grapes and they play important role in the fermentation process, converting the sugars of grapes into alcohol. There are also many commercial yeast strains which have different microbiological, chemical, physical and sensory aspects that need to be considered, when winemakers decide which yeast selection to choose, for making different wines. The most important yeast for the wine production is those belonging to the Saccharomyces genus, cerevisiae and bayanus species. The commercial yeast strains are sold in dry vacuum packages or liquid cultures. Dry yeast strains contain viable active yeast cells and they need to be properly prepared for inoculation into grape juice. This is very important step that will insure the yeast efficiency in the fermentation process. There are hundreds of different strains of yeast, which can be use in the winemaking process and each one has their own specific profile, function and characteristics.