Abstract: A multivalently interactive molecular assembly having a plurality of functional groups or ligands, in which a ratio between Rh and Rg expressed as Rh/Rg is 1.0 or less. Here, Rh is a hydrodynamic radius calculated from dynamic light scattering (DLS) assay performed in aqueous solution; and Rg is a radius of gyration determined based on the Zimm plot generated using data obtained by static light scattering (SLS) assay.