The Janus metastructure (JMS) is constructed in a special way so that the electromagnetic waves (EWs) propagate in the artificially constructed metastructure from different directions, which can show different electromagnetic characteristics and present a variety of functions at the same time. Its research is of great significance for breaking through the development bottleneck of traditional single-scale and single-function devices and can serve numerous novel application scenarios. This review discusses the design and research progress of JMS from three aspects: construction method, function realization, and application scenario. Finally, we discuss the key challenges currently facing the JMS and offer a vision for future research directions. We sincerely hope that this review will not only provide new insights into the development of JMS, which is a promising and dynamic hot research area but also promote research in this area from a more diverse and comprehensive perspective.

Design and research of the Janus metastructure