Properties of a material are determined by its structure,which has spurred lots of interest in attempts to produce new structures for achieving performance improvement of the material.In light of this,the birth of metallic glasses has triggered tremendous fundamental research on physical,chemical and mechanical aspects due to their distinct structure from the crystalline counterparts.Unlike nanocrystalline materials,metallic glasses usually have a uniform structure without long-range periodicity and characteristic structural constituents except for subnanometer-size clusters.It has long been believed that no interfaces associated with separate grains can be found in metallic glasses.Here we report on formation of such a new class of materials: nanogranular metallic glasses(NGMGs).A detailed study by X-ray diffraction and high-resolution transmission electron microscopy(TEM)documents the unique nanoscale granular structure of these materials.With nanoalloying immiscible metals in Fe-based NGMGs,the synthesized NGMG alloys show tunable ferromagnetism,electricity and mechanical properties.Formation of this new class of materials: NGMGs offers the opportunity to create non-crystalline alloys from these nanometer-sized components using a bottom-up approach.Our successful experimental testing of these NGMGs may open the way to new applications of MGs by means of novel material design in a wide range of technological areas.