A novel form of microcapsules, which possess single hollow cavities and thickness-controllable shells, were prepared by a two-step emulsification, emulsion ripening, and suspension polymerization. Parameters on morphology control of water-in-oil-in-water (W/O/W) emulsion globules were particularly investigated in this study, and a universal strategy to prepare single-core water-in-oil (W/O) globules from their multicore precursors was proposed. These single-core globules were further utilized as templates for solid microcapsules by the suspension polymerization, during which the phase-separation mechanism could be employed to form nanochannels across the shells. Such microcapsules could be further exploited as microreactors with functional cores to be loaded and would be especially suitable to encage bioactive materials.