The Center for Relativistic Laser Science (CoReLS) develops world-class, state-of-the-art laser technologies and conducts pioneering research on the generation and measurement of relativistic high-order harmonic attosecond pulses, as well as on stable electron and proton acceleration. Leveraging these technologies, we aim to experimentally realize strong-field quantum electrodynamics (SF-QED) phenomena under extreme conditions, such as collisions between relativistically accelerated particles and photons. Through this research, we seek to enable precise measurement and control of extreme physical processes and to provide theoretical insights for a deeper understanding of fundamental physics in such environments.