The prefrontal cortex is involved in a multitude of cognitive, emotional, motivational, and social processes, so exploring its specific functions is crucial for understanding human experience and behavior. Functional imaging approaches have largely contributed to the enhancement of our understanding, but might have limitations in establishing causal relationships between physiology and the related psychological and behavioral processes. Non-invasive electrical stimulation with direct or alternating currents can help to enhance our understanding with regard to specific processes, and might provide future protocols able to improve them in case of malfunctions. We review the current state of the field, and provide an outlook for future developments.