In this brief review, we look back on the conception of nano-atoms and their gradual evolutions into a new class of giant molecules in the context of soft matter science. The structural features and the characteristics about giant molecular self-assembly are summarized. It is found that these giant molecules with high conformational rigidities and precisely-defined shapes and symmetries can exhibit unusual phase structures and phase transition behaviors which are not commonly observed in conventional polymers. Their self-assembly is robust due to collective and cooperative interactions among nano-atoms, forming hierarchical structures that are sensitive to their primary structures. This modular feature is reminiscent to the domain concept in protein science. It is thus proposed that nano-atoms can serve as unique elements for macromolecular science.