ELyTMaX is an international joint unit (CNRS, Univ. Lyon and Tohoku Univ.), located both in Tohoku Univ. (Japan) and in Univ. Lyon. It is ruled as a French lab, in accordance with French and European regulations (incl. IP and expenses). Research at ELyTMaX focuses on behavior of materials and systems under extreme conditions (pressure, temperature…). An important activity is devoted to electromechanical energy conversion, including piezoelectricity and ferroelectric electrets. In the framework of FIESTA, ELyTMaX in in charge of modeling ferroelectric behavior (with LGEF), high electric field characterization of materials subjected to mechanical stress, and electromechanical structure (with C2N and LGEF).