The research group of Takeshi Yanai focuses on theoretical and computational investigation to describe chemical nature and reactivities of molecular systems by means of quantum chemistry (QC) calculations. The heart of chemistry lies in transformation of molecules. We view transformative molecules as what gives rise to beneficial transformations in chemistry, such as chemical reactions, functioning molecular properties, and so forth. The primal goal of our lab is to figure out mechanisms and principles of chemical transformation phenomena from the viewpoint that they are essentially driven by the role of electrons. In order to carry out this objective, our focus is also directed to investigation to develop advanced theory and algorithms of QC calculations, which are aimed at becoming tools that play a key role in synthetically developing the transformative molecules.