Abstract: Disclosed herein are multimeric molecular complexes and compounds that are multivalent, i.e., they have two or more targeting elements directed to a ligand that confers paracellular transporting properties and/or transcytotic properties to complexes and compounds to which it is bound. The complexes and compounds have properties that are different from the properties of monomers, complexes and compounds having only one targeting element directed to a paracellular and/or transcytotic ligand. The complexes and compounds of the invention undergo endocytosis, transcytosis and exocytosis; following endocytosis, the complexes or compounds may be transported into the cytosol or an organelle of a cell. In polarized cells, transcytosis can proceed in a “forward” or “reverse” direction. Reverse transcytosis is used for the non-invasive delivery of biologically active agents from the lumen of, e.g., the gastrointestinal tract or the airways of lungs, to the circulatory system.