In tongue inspection, the patient is in sitting position or dorsal position, facing the natural light. Open the mouth as wide as possible and extend the tongue outwards. Relax the tongue body and unfold the tongue surface. Let tongue tip down naturally. First, inspect the shape of the tongue body and the movement of stretching tongue. Second, inspect the colors of tongue tip, margins, center and root; inspect the features and colors of tongue fur, and then the sublingual veins.