Continuously glowing plasmas in solution can be obtained by applying a sufficiently high voltage (DC) between two gas-evolving electrodes of different sizes in an electrolyte, where the plasma is confined within a vapor layer surrounding the smaller electrode. While the effect was already observed in the middle of the 19th century, the first systematic studies in aqueous solutions only appeared in the middle of the 20th century. Today, this process is commonly denoted as Contact Glow Discharge Electrolysis (CGDE) or Plasma Electrolysis.