re: How do they make those little Cheerios?

Watch some food processing technology shows on the tube, they will give you insights as to how much mechanical manipulation is involved with what is bought at stores. All of the "puffed" grains that re in breakfast cereal boxes are cooked under a small amount of pressure which is then released in a second. PUFF happens. Dheerios are being extruded from a tiny orifice similar to that which makes "cake" doughnuts. A tiny amount of batter, as to the method of cooking, I don't have a clue, but I would go with a flash baking process.