Tongue moss is a Chinese medical term for a thin white and moist layer of moss called tongue moss on the back of the tongue in normal people. Tongue moss is composed of shed epithelium, saliva, bacteria, food debris, and exuded white blood cells. Under normal circumstances, due to the action of chewing and swallowing as well as the flushing of saliva diet, the material on the surface of the tongue can be continuously removed and only a thin white layer of tongue moss is manifested. However, if in case of disease, little food is eaten or only soft food is eaten, so that chewing and tongue movements are reduced, the tongue will become thicker. The normal tongue moss is thin and uniform, slightly thickened in the middle and root of the tongue, but if other diseases appear, it can cause a change in the color of the tongue moss. The sick tongue moss usually has white moss, yellow moss or gray-black moss, and sometimes green moss can occur, and it is common to see some plague, wet temperature or moldy sauce tongue, moldy sauce moss, red with black and yellow tongue moss. This is the basic situation about the tongue.