Tissue expansion is a relatively straightforward procedure that enables the body to "grow" extra skin for use in reconstructing almost any part of the body. A silicone balloon expander is inserted under the skin near the area to be repaired and then gradually filled with salt water over time, causing the skin to stretch and grow. It is most commonly used for breast reconstruction following breast removal-but it's also used to repair skin damaged by birth defects, accidents or surgery, and in certain cosmetic procedures.