Electrochemistry in small places and at novel interfaces is illustrated in the chapter. Secretory cells release chemical messengers to the extracellular space through a natural process called exocytosis. Different electrochemically detectable substances can be released from a variety of cell types by this process. Depolarization of the plasma membrane and a rise in intracellular calcium levels are hallmarks of the initiation of the exocytotic process. Electrochemical detection of exocytosis from single, isolated cells can be carried out in an amperometric or voltammetric mode. A number of chemical messengers released by neurons, neuroendocrine, and immune response cells are electrochemically active. These include dopamine, epinephrine, norepinephrine, and serotonin, all of which can be oxidized at moderate potentials. Chromaffin cells can synthesize, store, and release epinephrine and norepinephrine, while mast cells can only synthesize and release histamine. In mast cells, histamine is found in much greater quantity than serotonin. Microelectroporation-assisted insertion and careful micromanipulation of a micropipette is required for the formation of an artificial cell.