"THz radiation can penetrate through opaque dry materials. It is harmless and can be used to scan humans," Belyanin says. "Unfortunately, until recently the progress in THz technology has been hampered by a lack of suitable sources and detectors.""The highlight of our results is observations of interference of magnetoplasmons. By tiny changes in the applied magnetic field or temperature, we can make plasma waves amplify or cancel each other. This makes the whole sample either completely opaque or transparent to the incident THz radiation.