Multi-scaled microstructures induced by natural impurities (i.e., proteins, phospholipids, carbohydrates) in natural rubber (NR) were investigated by synchrotron small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and optical microscopy using several kinds of untreated and chemically treated un-vulcanized samples. These microstructures include large aggregates (size less than 50 mu m), well-defined crystals (size less than a few 10 mu m), and micelles (size much less than 10 mu m). In un-vulcanized NR samples, even though the concentrations of natural impurities are relatively low, the dispersion of these microstructures significantly affects the mechanical properties. (c) 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2456-2464, 2008