When making yeast breads, sugar, salt and warm water are added to the yeast, to stimulate growth and to help start the fermentation process. During the fermentation process gasses are released that cause the elastic structure of the flour to rise.
Because yeast does not like the cold, it is important that all ingredients used to make yeast breads be at room temperature, and that doughs should be allowed to rise in a warm area that is free of draft. Breads should be cooked quickly in hot ovens and allowed to cool on a way from any drafts.