Periodic structures have attracted interests of researches for decades, and they were discovered more and more useful properties, and have been applied to many fields. Furthermore, more and more novel concept and phenomena based on periodic structures were proposed and found, such as tunable electromagnetic properties of some structures. In this paper, recent progress on two of the periodic structures, i.e., FSS and metamaterials and their variations, were revie, and the physical nature of these structures analog to materials were also suggested.