The distinctive features of limited solubility in liquid eutectic and monotectic metallic systems have been discovered. The monodispersed emulsion model has been elaborated for a description of the specific microheterogeneous structure of eutectic melts. It includes the transitional shells (TS) at the interface boundaries having the eutectic composition and the closest packing of atoms. By means of the thermodynamic analysis a possibility of a metastable equilibriurn of the emulsion has been determined when dimensional and interface energy parameters of the emulsion adopt certain values. The metastable state is characterized by the colloidal sizes of disperse particles and the interface tension values typical for immiscible melts. The existence of the emulsion has been confirmed by the calorimetric experimental data on Sn-Pb and Al-Si systems. Structure factors and RDF's of the TS have been calculated by the original treatment of experimental diffraction data on Sn-Pb and Ag-Ge melts. The evidence of different microheterogeneity scales in liquid eutectic and monotectic systems has been obtained. From two immiscible phases only the liquid based on the light-melted metal shows the short-range microinhomogeneity and the second one is a homogeneous solution. So, the microheterogeneity in eutectic and monotectic melts has different nature.