Various materials such as metals, semiconductors, oxides, and organics matters can be characterized by their physical and chemical properties, such as electronic conductivity, optical properties, and chemical reactivities, which exhibit variations over wide ranges. In order to utilize those properties in our life, it is desirable to produce materials with preferable properties by modifying their microscopic structures. To this end, it is of crucial importance to clarify the mechanisms underlying their physical and chemical properties. We are developing computational techniques based on quantum mechanics (first-principles methods). The forefront methods are applied to real materials to study their properties, and even to hypothetical structures to design new materials. Based on the obtained knowledge, we extract ideas to design new materials with desired properties. We are collaborating with experimental groups to prove our predictions. Through our researches, we wish to contribute to our society in terms of researches of clean and efficient energy resources, environmental protection, and development of industries.