This chapter describes the major goals that must be achieved and the some progress in the realization of the tremendous potential of human embryonic stem cells for clinical medicine. Safety considerations will be of major importance in bringing Embryonic Stem (ES) cell-related therapies to clinical application. There are several major areas of safety concern including the potential for transmission of infectious diseases and a myriad of tissue type-specific adverse outcomes. Tissue engineering can be broadly defined as the application of the principles of life sciences and engineering to generate biological substitutes to replace or support the function of defective or injured body parts. Operationally, this might entail combining one or more different cell types with one or more different polymer matrices to form a defined shape and perform a specific function. A number of animal studies have used a variety of donor cell types to test the effect of cell therapy in injured cardiac muscle with promising early results.