Controlled trapping atom-precise ultrasmall silver nanoparticles into silver nanoclusters is challenging; thus only limited progress has been made in this area. We are therefore inspired to isolate two novel silver nanoclusters, Ag10@Ag70 (SD/Ag80a and SD/Ag80b; SD = SunDi), where a novel fcc-structured Ag10 kernel built from two single-edge opened Ag6 octahedra by sharing one edge is trapped. The bioctahedral Ag10 kernel is locked by a pair of Mo7O26 10- anions to form an inner Ag10@(Mo7O26)2 core which is further encapsulated by an outer Ag70 shell to form three-shell Ag10@(Mo7O26)2@Ag70 nanoclusters. Notably, the bioctahedral Ag10 kernel has not been observed in silver nanoclusters ever before, thus representing a new embryo state of silver nanoparticles. SD/Ag80a emits in the near infrared (NIR) region (λ em = 730 nm) at low temperature. This work will deepen our understanding on the atomic-level growth of silver nanoparticles and complicated three-shell self-assembly involving polyoxometalate (POM) and two different silver nanoclusters.