  Embedded clusters, which are embedded in bulk materials and different from
the surroundings in structures, should be common in materials. This paper
studies resonance of such clusters. This work is stimulated by a recent
experimental observation that some localized clusters behavior like fluid at
the mesoscopic scale in many solid materials [Science in China(Series B). 46,
176 (2003)]. We argue that the phenomenon is just a vivid illustration of
resonance of embedded clusters, driven by ubiquitous microwaves. Because the
underlying mechanism is fundamental and embedded structures are usual, the
phenomenon would have great significance in material physics.
