The invention relates to a method for permeabilization of a cell structure consisting of a single cell, an intracellular structure or an organelle comprising the following steps: (a) microelectrodes, preferably two carbon fiber electrodes or hollow fiber electrodes, are provided, (b) the microelectrodes are connected to a power supply, (c) the electrodes, individually controlled by high-graduation micromanipulators, are placed close to the cell structure at an appropriate inter-electrode distance, and (d) a highly focused electric field of a strength sufficient to obtain electroporation is applied between the electrodes. The method may be used in order to transfer cell impermeant solutes, such as drugs or genes, into the cell structure or out of the cell structure, in biosensors, in the treatment of tumours and neurodegenerative diseases and in the study of biophysical processes.