The possibility of nanomodification of eutectic alloys by fast heating slightly above eutectic temperature with subsequent very fast cooling or just quenching is analysed. The basic physical effect that may be a basis of such a ‘thermal prick’ idea is the following: (1) short-time contact melting of any inter-phase interface leads to the formation of a thin liquid layer instead of a parent solid–solid interface; (2) fast cooling of this thin liquid layer proceeds under the step of composition between opposite boundaries. Therefore, the phase transformation should be in an open inhomogeneous system. In many cases, crystallization is reduced to decomposition under the external composition gradient and demonstrates quasi-periodic phase formation with nanometre separation distance. It means that the special heat treatment, which we call the thermal prick, may create additional nanostructured zones around each interface within the parent eutectic alloy.