Tissue engineering is a biomedical engineering subject that restores, maintains, improves, or replaces biological tissues using a combination of cells, engineering, materials technologies, and appropriate biochemical and physicochemical parameters. Tissue engineering is most commonly associated with the use of cells on tissue scaffolds in the development of new living tissue for medical purposes, however it is not restricted to cell and tissue scaffold applications. While it was originally considered a sub-field of biomaterials, it has grown in scope and importance to the point that it may now be regarded a separate field. Tissue engineering/regenerative medicine strategies necessitate the interaction and integration of suitable physical and biological signals with tissue and cells. As a result, modifying variables such physiologically active proteins and DNA are essential for success. Simpler methods, such as employing primary chondrocytes to replace damaged cartilage and skin cell sheets to replace damaged skin, are now more successful. However, certain larger and more sophisticated tissue reconstructions, most notably the bladder, have been completed successfully, indicating that more complex tissue engineering operations may be possible in the future.