X-ray diffraction studies have been carried out on stratum corneum (SC) intensively. The results provide an evidence for the relationship between the microstructure and the characteristic of SC. In this paper, based on the microscopic evidence, we will show first the characteristic of the barrier function of SC, second the relationship between the barrier function and the structure of SC, and third the reconstitution of the damaged SC when it is immersed in a dilute aqueous suspension of mixture of ceramide, cholesterol and fatty acid that are dominant components in the intercellular lipid matrix.