Abstract: A phase transformational cellular material, including a plurality of bistable cells, each respective bistable cell operationally connected to at least one other respective bistable cell. Each bistable cell enjoys a first stable phase and a second stable phase. The first stable phase is a first geometric configuration and the second stable phase is a second geometric configuration different from the first geometric configuration. An energy transaction is required to shift each respective cell between stable phases. A mechanical energy transaction is required to shift from the first to the second phase, while a thermal energy transaction is required to shift from the second to the first phase.