The primary ingredient in the process of making flour is grain, specifically wheat. Wheat grains are harvested, cleaned, and then milled down to produce flour. Different types of flour can be made from various grains, like rye, corn, or barley, depending on desired use. Wheat flour is the most common because it contains gluten, which provides elasticity and strength to baked goods. The milling process involves grinding the grains and sifting them to achieve the desired coarseness or fineness. Different flour types (like all-purpose, whole wheat, or bread flour) are used based on baking needs, impacting texture and taste significantly.