Metal-organic cages (MOCs) represent a tantalizing class of metal-organic materials (MOMs) in terms of host-guest binding ability related to their well-defined cavities and engineered pores. Herein, we highlight the synthesis of MOCs and their post-assembly modification (PAM) reactions. Unlike discrete MOCs, infinite cage-based frameworks that use MOCs as supramolecular building blocks (SBBs) will be discussed. Finally, we address the solubility and stability of MOCs as significant prerequisites for favoring the high-order assembly into extended structures.