After keeping your hair unwashed for 2-3 days, concentrate on combing your hair thoroughly once, standing in front of a desk while combing, with your head down so that all the hair shed during combing can fall on the desk until no hair continues to fall out. Collect and organize these hairs and paste them in the following form: please put the hair roots facing up and 1-2cm beyond the edge of the transparent tape. count the total number of hairs after pasting and record them on this paper. Note: It must be all the hairs shed, do not miss those tiny hairs when collecting them.