We have demonstrated selective transfer of membrane-impermeant solutes into single cells by using a miniaturized version of electroporation. The technique might become valuable for basic and applied studies of electroporation on the single-cell and organelle level. Further miniaturization of the technique by using nanotip electrodes with insulated shanks that can be inserted into a cell for exclusive electroporation of organellar structures with minimal impairment of cellular physiology would be feasible. The methodology is compatible with a wide range of biochemical and biophysical techniques and chemical microseparation formats that operate on the single cell and single organelle level (see refs. 1-10). It contrasts microinjection techniques for single cells and single nuclei in that it can be timed precisely and applied to biological containers of sizes much smaller than can be resolved in a light microscope.