Polyion complexes (PICs) are attractive as eco-friendly materials, because they offer simple and fast preparation methods to exert various functionalities in aqueous medium. However, control of nanoarchitectures in PIC materials has not been fully realized, except for the case of micelles and unilamellar vesicles formed from block ionomers. Here, the procedure to control PIC nanoarchitectures with various morphologies was established for the first time by careful tuning in the composition of PICs made from PEG-based block-ionomers with a varying amount of homoionomers as additive to modulate the PEG weight fraction (f(PEG)) in the obtained PICs. Accordingly, the variation in f(PEG) from 12.1% to 6.5% induced vigorous transition in the microphase separated structures of PICs basically from micelle to lamella via cylindrical network. Notably, uniformed lamella with alternative layers of PEG and PIG domains was found at elevated temperature (70 degrees C), which, by lowering temperature, reversibly transformed to cylindrical P1C network apparently with connected aqueous channel in mesoscopic scale.