Conventional processing of functional materials in the form of electroceramics normally involves several steps that include calcination of the reagent-grade raw materials at a relatively-low temperature for synthesis of the end-product powder, followed by grinding to reduce particle size, compaction to get a reasonable green density, and finally sintering at a high temperature for densification. Introduced in the literature in 2010 is a novel approach known as flash sintering, which is assisted by an electric field, and whose main characteristics is that high-density electroceramics can be produced from green compacts in mere seconds, at furnace temperatures well below those required in conventional sintering. This technique has become largely explored in materials processing, and much of the effort includes advancing, as much as possible, the debate on the underlying mechanism(s). This talk aims to present results observed not only in single-phase powders, with a review of the effects of electric field strength and current density, but also in multi-phase powders where flash synthesis plus sintering, called reactive flash sintering, can develop in a single running experiment. Particularities and generalities applying in both scenarios will be discussed, including the case of ionic conductor/insulator composites where percolation effects may become the determining key.