The interest in the methods of sintering under external fields (electric, magnetic, mechanical - field assisted sintering technology - FAST) increases exponentially in the world. For two decades, spark-plasma sintering (IPS), microwave sintering (MI), flash-sintering (FS), or thermal runaway - "flash" - have been significant progress. This trend is due, first of all, to the fact that the combination of electric, magnetic and mechanical fields creates a flexible instrument for the fine control of the structure and properties of materials. Nanocomposites with ceramic matrix attract great attention, because they allow us useful combination of properties inherent in their components in one material. The SPS provides several approaches to obtaining nanocomposites of different types of matrix: 1) sintering of pre-mixed nanopowders, 2) reactive sintering of mixtures of reactant powders, and 3) sintering of pyrolysis products of polymers under the SPS mode. Known modifications of the method such as reactive spark-plasma sintering is valid to generate multiphase system where spatial factor limiting the grain growth. Slow growth of grains in the process of SPS may be due to: 1) intense heating in the initial stages of sintering, which prevents the coalescence of grains; 2) pinning the boundaries of grains with nanosized grains of other components; 3) competition between nucleation and nuclei growth in reactive sintering; 4) extremely low driving force of grain growth in an ensemble of mono-sized crystallites dispersed in an amorphous matrix. These phenomena will be presented in the paper. Conducting and non-conducting dense composites have been experimentally obtained under SPS conditions. Micro / nanocomposites based on high melting compounds will be presented.