Electroporation is a phenomenon during which exposure of a cell to an electric field results in a significant increase in its membrane permeability. Reversible electroporation is widely used for internalisation of various substances in research, and is also becoming important in clinics (tumor electrochemotherapy). Electroporation is explained as formation of nanometer-sized aqueous pores in the lipid bilayer due to increased membrane voltage caused by an electric field. This explanation is also supported by molecular dynamics simulations of the lipid bilayer. The pores are too small for electroporation to be observable directly, but it can be studied by measuring the electrical and optical properties of the membrane, or by monitoring the flux of ions or molecules through the membrane. The fraction of electroporated cells and the uptake increase with the increase in the strength, duration and/or number of pulses, but so does the fraction of cells that lose viability. For optimal results under specific experimental conditions, the values of pulse parameters must be determined under these same conditions.