Dendrimers constitute a class of polymers with unique properties and applications resulting from the presence of internal voids and of a large number of functionalities on the surface. The development of a macromolecular chemistry within the cavities of dendrimers is illustrated here. Two examples of construction of six dendrimer units within the cascade structure of a main dendrimer are reported. The preparation of these multidendritic systems involves the regioselective modification of the framework of the central dendrimer to create internal reactive centers, followed by the stepwise synthesis of the six dendritic macromolecules.