electromagnetic (em) absorbers play an increasingly essential role in the electronic information age, even toward the coming “intelligent era”. the remarkable merits of heterointerface engineering and its peculiar em characteristics inject a fresh and infinite vitality for designing high-efficiency and stimuli-responsive em absorbers. however, there still exist huge challenges in understanding and reinforcing these interface effects from the micro and macro perspectives. herein, em response mechanisms of interfacial effects are dissected in depth, and with a focus on advanced characterization as well as theoretical techniques.