Injera, the staple food of Ethiopians is made from a tiny, iron-rich teff seeds ground into flour. The production of this crop is usually limited to certain middle elevations with adequate rainfall as it is a low yield crop and expensive for an average household to grow. Many Ethiopian highland farmers grow their own subsistence grains such as wheat, barley, corn or rice flour in replacement of teff content. Teff seeds are graded according to color, depending on how they are used to such as to make different kinds of injera: nech (white), key or quey (red), and sergegna (mixed). Teff flour is also gluten-free.