A method of introducing a structure, such as a hole or cavity or channel or well or recess, or a structural change, such as a transition from a crystalline structure to an amorphous structure, in a substrate or a region thereof, said method comprising the steps: a) providing a substrate which is electrically insulating or semiconducting at room temperature, and placing it between at least two electrodes (3; 3')connected to a user-controlled voltage supply, b) applying, by means of said user-controlled voltage supply, a voltage of user-defined magnitude across a region of said substrate, said voltage being sufficient to give rise to an increase in electrical current through said substrate or said region, thereby applying a defined amount of electrical energy to said substrate, c) applying additional energy, preferably heat, to said substrate or said region so as to increase the temperature and the electrical conductivity of said substrate or said region so as to initiate the current flow in step b), said additional energy, preferably heat, originating either from an additional energy or heat source or from components of said voltage applied in step b), d) dissipating said electrical energy applied in step b) in said substrate, wherein step d) is controlled solely by (i) the user-defined magnitude of the applied voltage of step b), (ii) a user-defined period of time of step b), (iii) an impedance of said voltage supply, or (iv) any combination of (i) - (iii), and characterized in that said substrate is provided in step a) having at least one electrically insulating layer attached, which is solid at room temperature, and further characterized in that said electrically insulating layer has an insulating region which is adjacent to and in contact with said substrate region in which substrate region a structure or structural change is to be introduced, wherein step c) is performed such that said electrically insulating layer is liquefied in said insulating region, and wherein during step d), said electrically insulating layer is partially displaced in said insulating region, through the dissipation of said electrical energy, and wherein, after step d), said liquefied electrically insulating layer flows into said generated structure and thereby closes and at least partially fills said structure. a) providing a substrate which is electrically insulating or semiconducting at room temperature, and placing it between at least two electrodes (3; 3')connected to a user-controlled voltage supply, b) applying, by means of said user-controlled voltage supply, a voltage of user-defined magnitude across a region of said substrate, said voltage being sufficient to give rise to an increase in electrical current through said substrate or said region, thereby applying a defined amount of electrical energy to said substrate, c) applying additional energy, preferably heat, to said substrate or said region so as to increase the temperature and the electrical conductivity of said substrate or said region so as to initiate the current flow in step b), said additional energy, preferably heat, originating either from an additional energy or heat source or from components of said voltage applied in step b), d) dissipating said electrical energy applied in step b) in said substrate,