Devices used to generate extra soft tissue in vivo to be used in surgical reconstructions. They exert stretching forces on the tissue and thus stimulate new growth and result in tissue expansion. They are commonly inflatable reservoirs, usually made of silicone, which are implanted under the tissue and gradually inflated. Other tissue expanders exert stretching forces by attaching to outside of the body, for example, vacuum tissue expanders. Once the tissue has grown, the expander is removed and the expanded tissue is used to cover the area being reconstructed.