Аннотация:Humic substances (HS) are self-assemblies of natural polyelectrolytes occurring throughout the environment. They have been known to play important biospheric roles by mediating uptake of nutrients by plants, regulating biogeochemical cycles of elements, mitigating adverse impact of contaminants, and structuring soils. Until recently, it was believed that these are mostly molecular (complexing) interactions which drive substantial impact of HS on stability of colloids, bioavailability of nutrients, and toxicity of contaminants. The advent of nanotechnology supplied new tools for exploring mechanisms of HS interactions with metals and metal oxides on molecular and nanoscale. The new findings unraveled a great potential of HS in the field of matrix-assisted synthesis of metal-containing nanoparticles (NPs). This chapter gives examples of those syntheses for producing NPs with superparamagnetic properties and of enhanced bioavailability to plants, which demonstrates potential for a transfer in technological applications.