A pre-ferment (pâte fermentée), also calle a "sponge" or a "bread starter", is a fermentation starter used in bread baking. It usually consists of a simple mixture of flour, water, and a leavening agent (typically yeast or yogurt), and is added to bread dough before the kneading and baking process as a substitute for yeast. Though they have declined in popularity as direct additions of yeast in bread recipes have streamlined the process on a commercial level, pre-ferments of various forms are widely used in artisanal bread recipes.