Bill demonstrates the temperature-dependent shape memory of nitinol metal. He explains how "twinning" in the crystal structure of nitinol produces the memory effect. He shows a nitinol-based engine that is powered by temperature differences. He closes the video with a description of superelasticity, a phenomenon related to the memory effect, which he demonstrates with a cardiac stent. (This video is dedicated to my second son: born right after the rough draft was finished, and who, thus, delayed the filming of the final video by eight months.)