Lightweight and strong materials play an important role in the development of novel materials for construction, aerospace, and implant applications. These materials can be implemented using modular building units that can be assembled into aimed interconnected structures. This study uses a hierarchical design strategy to demonstrate a new class of lightweight and strong carbonaceous closed cellular structures. In contrast to conventional top-down approaches, building units are prepared by multiscale design approach starting from a synthesis of functionalized graphene oxide nanosheets at molecular- and nano-scale, stepping up into microfluidic fabrication of solid-shelled bubbles with shape diversity at micro-scale. Then, the microscale solid bubbles are strategically assembled into three-dimensional (3D) structures, subsequently transforming into self-interconnected and structurally-reinforced closed cellular structures through post-treatment, finally leading to a generation of 3D rhombic dodecahedral honeycomb lattice in centimeter scale. The finally obtained ordered structure exhibits an elastic modulus above 500 kPa, while maintaining a low density of 9.8 mg/cm3, opening a new path of lightweight and strong structured materials.