This review focuses on a class of unconventional macromolecules-giant molecules based on nano-atoms. Nano-atoms are 3D molecular nanoparticles (MNPs) with rigid shapes, well-defined chemical structures, and specific symmetries. Giant molecules are precise macromolecules built from molecular nanoparticles. Inspired by the domain concept in proteins, we propose that MNPs can serve as the structural and functional domains for synthetic macromolecule, allowing one to design and synthesize materials with the desired function in a modular fashion via the retro-functional analysis. The structure-property relationship gained from this process will improve our understanding of these materials and guide the optimization of the materials property. Giant molecules can also be viewed as size-amplified small-molecule analogues, exhibiting similar but also distinct self-assembly behaviors from their counterparts. For example, giant surfactants behave like small-molecule surfactants in solution, forming micelles with stretched tails and versatile morphologies, but assemble into nano-phase-separated structures in bulk just like block copolymers. Their self-assembly exhibits unusual sensitivity to the primary chemical structures and the formation of unconventional hierarchical structures is not uncommon, including the Frank-Kasper phases, the non-integral folding in low molecular weight PEO lamellar crystals and various hierarchical structures in solution self-assembly. Therefore, we envision that giant molecules will be technically very important and receive numerous practical applications in the near future.

Contents
1 Introduction
2 Giant molecules: the domain concept
3 Retro-functional analysis: structural synthon and functional synthon
4 Giant molecules: precision synthesis
4.1 Click chemistry
4.2 Molecular nanoparticles
4.3 Sequential click chemistry
5 Giant molecules: controlled assembly
6 Conclusion and outlook