The complete physiological process of hair follicles consists of two basic phases,i.e.,embryo follicle morphogenesis and mature hair follicle cycling.Hair follicles come from ectoderm cells.Besides,the location and morphological characteristics of hair follicles have been determined during the process of embryonic development.Once the hair follicle is formed,it goes into the cycling following external stimuli.Hair follicle cycling includes anagen,catagen and telogen.Generally,the morphogenesis and maintenance of cycling of follicles are regulated by a series of complicated signaling pathways,including Wnt,transforming growth factor-β/bone morphogenetic protein,Hedgehog,fibroblast growth factor,Notch,epidermal growth factor,and so on.