Cassette electrophoresis systems that allow viewing of molecules during the electrophoresis run are disclosed. Cassette electrophoresis bases that reversibly engage light sources, such as light source bases are disclosed. Also disclosed are visible light transillumination systems for viewing a pattern of fluorescence emitted by fluorophores comprising a cassette housing fluorophore-containing material and a base unit to support the cassette. In some aspects the base unit that includes a power supply also houses a light source having output in the visible wavelength region and a filter placed between the light source and the fluorophores. The system is constructed and arranged such that patterns of fluorescence emitted by the fluorophores are viewable. Also described are charging devices for providing charge to gel electrophoresis systems, portable gel electrophoresis systems and methods of use thereof.