Subcutaneous fat layer. According to query 39, the facial skin is slack, and the first slack layer is subcutaneous fat layer. If the subcutaneous fat layer shrinks in dispute, the skin will sag. There will be displacement, atrophy and fat reduction of deep fat pad in the middle of the face, and sagging in the middle of the face. Skin laxity performance index, primary index: prominent pores, intermediate index: blurred facial contour, and advanced index: laxity and sagging.