Native to the warm Mediterranean regions, oats have been cultivated for thousands of years as a source of food and folk remedies. Today, the oat plant (Avena sativa) is most famous for the nutritious cereal grain that it provides–think morning oatmeal. However, the whole plant, referred to as oat straw, gathered when the grains are ripe, includes also the leaves, stems. The whole plant is then dried and chopped, and used in both internal and external forms by traditional herbalists. The grain itself, harvested in late summer, is milled to produce oatmeal and oat bran. Oatmeal, the ground grain, has a high silica content, and can be used externally for skin problems. Oat bran, produced from the coarse husks of the grain, is good at reducing cholesterol levels.