Finally the cleaning process is accomplished using air blown on the grain or plant. The plant sits on a screen and air is blown on it forcefully. This separates and blows away lighter bits of plant material, called chaff, which may still be clinging to the grain. The grain then goes into a collecting tank. When the collecting tank is full of clean grain, it is shot out of a pipe called an unloader, into a storage bin or trailer attached to the combine harvester.