1. A method of delivering pharmaceutical drugs and/or therapeutical substance, comprising nucleic acids and protein molecules to a mammal in vivo comprising: - injecting a molecule and stimulating delivery of said molecules with an electrical current wherein said molecules are injected into a skeletal muscle - positioning electrodes near the injection site such that the current travelling through the electrodes passes through the injection site; and - electrically stimulating the muscle with an electrical current having a field strength between 25 V/cm and 200 V/cm. 2. The method of claim 1 wherein said electrical stimulation is delivered in the form of a single square bipolar pulse. 3. The method of claim 2 wherein said bipolar pulse has a duration of between about 50 μs and 5000 μs. 4. The method of claim 1 wherein said electrical stimulation is delivered in the form of between about 2 to 30.000 square bipolar pulses. 5. The method of of claim 4 wherein said bipolar pulses have a total duration of between about 10 ms to 12.000 ms. 6. The method of claim 5 wherein said bipolar pulses are delivered in the form of at least two trains. 7. The method of of claim 6 wherein the frequency of said electrical stimulation is between about 0,5 Hz and 1000 Hz. 8. The method of claims 1 to 7 wherein said molecule is a nucleic acid, said nucleic acid operably linked to a promoter which directs the expression in said muscle cells of the protein coded by said nucleic acid. 9. The method of claim 8 wherein the nucleic acid is a single-stranded nucleic acid. 10. The method of claims 1 wherein the electrical field is provided in a step-wise manner. 11. The method of claims 1 to 10 wherein the electrical field is positioned with its field lines approximately across the fibers of the muscle. 12. A method of genetically immunizing a mammal by transfecting a nucleic acid into the skeletal muscle of said mammal in vivo comprising: - injecting a skeletal muscle of a mammal with a nucleic acid operably linked to a promoter which directs the expression of said expression in said muscle of the protein coded by said nucleic acid; - positioning electrodes near said nucleic acid injection site such that the current travelling through the electrodes passes through said nucleic acid injection site; and - stimulating the muscle with an electrical current having a field strength between about 25 V/cm and 200 V/cm. 13. The method of claim 12 wherein said electrical stimulation is delivered in the form of a single square bipolar pulse. 14. The method of claim 13 wherein said bipolar pulse has a duration of between about 50 μs and 5000 μs. 15. The method of claim 12 wherein said electrical stimulation is delivered in the form of between about 2 to 30.000 square bipolar pulses. 16. The method of claim 15 wherein the sum of the pulse durations of said bipolar pulses is between about 10 ms to 12.000 ms. 17. The method of claim 16 wherein said bipolar pulses are delivered in the form of at least two trains. 18. The method of delivering a molecule of claim 17 wherein the frequency of said electrical stimulation is between about 0,5 Hz and 1000 Hz. 19. The method of claim 12 wherein the nucleic acid is a single-stranded nucleic acid. 20. The method of any claims 12 to 19 wherein the electrical field is provided in a step-wise manner. 21. The method of any claims 12 to 20 wherein the electrical field is positioned with its field lines approximately across the fibers of the muscle. 22. A method of systematically delivering a protein in a mammal comprising: - injecting a muscle of a mammal with a nucleic acid operably linked to a promoter which directs the expression in said muscle of the protein coded by said nucleic acid; - positioning electrodes near said nucleic acid injection site such that the current travelling through the electrodes passes through said nucleic acid injection site; and - stimulating the muscle with an electrical current having a field strength of between 25 V/cm and 200 V/cm. 23. The method of claim 22 wherein said electrical stimulation is delivered in the form of a single square bipolar pulse. 24. The method of claim 23 wherein said bipolar pulse has a duration of between about 50 μs and 5000 μs. 25. The method of claim 22 wherein said electrical stimulation is delivered in the form of between about 2 to 30.000 square bipolar pulses. 26. The method of claim 25 wherein the sum of the pulse durations of said bipolar pulses is between about 10 ms to 12.000 ms. 27. The method of claim 26 wherein said bipolar pulses are delivered in the form of at least two trains. 28. The method of claim 27 wherein the frequency of said electrical stimulation is between about 0,5 Hz and 1000 Hz. 29. The method of claim 22 wherein the nucleic acid is a single-stranded nucleic acid. 30. The method of any claims 22 to 29 wherein the electrical field is provided in a step-wise manner. 31. The method of any claims 22 to 30 wherein the electrical field is positioned with its field lines approximately across the fibers of the muscle. 32. Device for making cell-tissue susceptible to the delivering of a pharmaceutical or therapeutical substance, said device comprising: a voltage-controlling apparatus capable of delivering an electrical field with a field strength of 25 V/cm - 200 V/cm; electrodes suitable to be placed around a body part of a mammal and capable of providing the electrical field to the relevant body part, wherein the voltage-controlling apparatus is adapted to further forming, in alternative regimes, the electrical field in a step-wise manner or in the form of a single square bipolar pulse.