In the past, for skin scars, moles, hemangiomas and other plastic repair, mainly rely on autologous tissue transplantation, so some people call plastic surgery is “tearing down the east wall to patch the west wall.” Sometimes for smaller skin scars can be used once excision or stitching method, although the surgical effect is more ideal; but a little larger, especially the face, head and other slightly larger scars can only use the method of skin grafting. Although implantation has the effect of improving the appearance of scars, but due to a series of problems such as skin color and skin edge scars after implantation, even if the implanted skin pieces survive well, it will not bring much improvement to facial beauty. The plastic principle of the tissue expander is to provide “extra” soft tissue to the skin. The expander is a capsule made of silicone rubber film, which is surgically implanted under the skin or submuscular layer, and the tissue is expanded by injecting sterile isotonic saline into the injection jug periodically through the skin. After a certain period of expansion, the soft tissue of the skin on the surface of the dilated capsule gradually stretches and expands, providing approximately 50% or more “extra” skin tissue. The advantage is that the “extra” skin tissue provided by this tissue expander is similar or identical to the skin around the defect area in terms of color, texture, thickness, hair distribution, and aesthetics, and also It also has the characteristics of good blood flow and sensation. Tissue expansion is usually performed in two stages. The first stage of the procedure is dilator implantation. After removal of the stitches, sterile saline is regularly injected through the skin by puncture and through an injection jug. The time required for dilation is usually 3-6 months, 1-2 times per week. The skin should be expanded to twice the size of the defect area to repair the defect and close the donor wound. After the skin is expanded to the desired level, the second stage of surgery can be performed, i.e., the tissue expander is removed through the original incision, the scar or diseased tissue in the defect area is excised, and the skin that has been expanded to a certain level is advanced or rotated to the defect area, and the whole procedure is completed by plastic suturing. The figure below shows a case of a nevus on the waist, in which a dilator was implanted in the normal skin around the nevus and injected with water, the dilator was removed in the second stage and the nevus was completely excised and the incision was closed.