Dyes and other charged materials can be injected into small cells by iontophoresis. The iontophoresis micropipette should have a tip resistance of 30-100 MΩ. Injection current is about 5 nA (negative DC current). Since iontophoresis is mainly used for injecting small cells (5-20 μm in diameter), the injection device is set up on a compound microscope (upright with water-immersion lens or inverted). The injection can be monitored with weak epi-fluorescence illumination. One can simply use single wavelength LED as the source of epi-illumination or replace mercury arc or metal-halide lamp in the light hub with a regular lamp normally used as transmitted light source.