Langer and Vacanti characterized tissue engineering (TE) in the early 1990s as "an interdisciplinary area that uses engineering and life science ideas to the development of biological substitutes that restore, maintain, or improve tissue function". The goal of TE is to trigger tissue-specific regeneration mechanisms, overcoming the well-known difficulties of organ transplantation (i.e., donor shortage, need of immunosuppressive therapy). Biomaterials are essential in tissue engineering because they allow cells or growth agents to be delivered efficiently. Biomaterials can be used as carriers to transport cells to a desired location and induce local tissue regeneration, as barriers to protect transplanted cells or tissues from host immune response, or as reactors to drive host cell recruitment, homing, and differentiation. An optimal biomaterial for tissue engineering should have a high cell survival rate, proper cell function after transplantation, and the ability to promote autologous functional tissue growth in situ, as well as its own deterioration when therapy is completed.