Active dry yeast comes in the form of small granules or spherules. This yeast is characterized by good stability and keeps well in regions where climatic conditions are difficult. It must be first diluted in a little lukewarm water or milk. Instant dry yeast like Saf-instant is made up of tiny vermicelli that can easily be incorporated into the dough. To maintain their effectiveness, instant dry yeasts are packaged in a vacuum or in a protective atmosphere. They must be kept dry at room temperature.