In order to optimize mass transportation and exchange, nature creates hierarchically porous networks whicharecomposedofmulti- levelbranches.Althoughbottom-uptemplatingmethodshavesucceeded in fabrication of these kinds of hierarchically porous networks, the templates have to be assembled/packed in advance, therefore, driving the fabrication process too complex. In this report, we presented that the hierarchically porous networks could be fabricated through migration of templates, which was similartoformationofrivers.DuringthermalpyrolysisofPrussian bluecages,theinsitulygeneratediron oxides nanoparticles diffused and aggregated together to grow larger, and eventually moved outside from the porous carbons. The moving routes of the iron oxides became hierarchical channels in the obtained carbon cages. By using the porous carbon cages as electrode for Na–ion battery, a pseudocapacitor-type ion storage was investigated.