Ultrathin, mechanically flexible, and stretchable electronics are essential elements for the realization of new electronic devices. In particular, they are becoming increasingly important in medicine, healthcare, nursing care, and robotics. However, it is not easy to achieve both mechanical flexibility and electrical stability and reliability. In this seminar, Sekitani will introduce the research background, objectives, current state-of-the-art research and applications, remaining issues, and future prospects of electronics with ultimate thinness, flexibility, and stretchability.