Recent structural research on humics exploiting very high resolution electrospray ionization mass spectrometry and high field multidimensional, multinuclear NMR is reviewed to afford an intimate view of humic mixtures. From this perspective we recognize the complex pattern of labile aggregational and conformational equilibria under the influence of weak forces (H-bonding, hydrophobic interaction, charge transfer complexing) that characterize such mixtures. Those patterns closely match the definition of a dynamic combinatorial system (DCS). New data from water proton NMR relaxation times in the presence of humic acid and Cu2+ and kinetics of Cu2+ release derived from competing ligand exchange (CLEM) studies are interpreted in terms of such equilibria. The concept of dynamic combinatorial systems is applied to strong binding of Cu2+ to test for the importance of DCS aggregational and conformational equilibria in complexation