Crying or shedding tears is one way to express emotions. But behind his emotional impression, it turns out there are some interesting facts about tears that are not widely known. Tears are produced by the lacrimal glands in the upper eyelid. In addition to venting emotions, it turns out tears also play an important role in maintaining eye health, such as to moisturize the eyes to prevent dry eyes and irritation, and provide nutrition to the eyes. Tears Consist of Several Layers Tears consist of three layers. Each tear layer contains various nutrients, such as potassium, sodium, protein, glucose and fat. These nutrients will later be used to protect and lubricate the surface of your eyes. Here are the layers that are in tears: A layer of water This is the thickest layer in the structure of tears. The layer of water serves to remove impurities that enter the eye, moisturize the eye, and protect the cornea of the eye. Oil coating This layer contains more fat. This large amoun...