Investigation of developmental potential of various embryonal tissues is important for design of new approaches to regenerative medicine aimed at supplementing tissues damaged by trauma or disease. Rodent embryos have been extensively used in experiments designed for investigation of developmental potential to give rise to various types of epithelia such as superficial epithelia, neuroepithelium and sometimes even malignantly transformed epithelium in teratoma-like structures. These experiments have been done in vitro, in transplants in vivo and by combined in vitro-in vivo methods.