Porous cage-like molecules are often formed through the 2 bottom-up self-assembly of building blocks with varying con-3 nectivities and geometries, which transfers into the properties 4 of the cage. The broad term "cage" applies to macrocyclic 5 structures containing an intrinsic void widely exploited for 6 various types of applications, e.g. catalysis, 2 sensing, 3 separa-7 tions, and as porous liquids. Their bottom-up self-assembly 8 affords a vast pool of building blocks, allowing for the tunabil-9 ity of their properties. Cages can be entirely organic (porous 10 organic cages, POCs) or contain metals (metal-organic cages, 11 MOCs). Through rational selection from this vast chemi-12 cal space and control of the self-assembly outcome and cage 13 structure, researchers can achieve fine control over the spatial 14 arrangement of atoms inside and outside cage compounds.