With the advance of nanoscale electrodes, the resolution of SEE has advanced from being able to detect single cells to detecting single molecules within cells. Nanoscale electrodes are small enough they can be inserted into the synapses between neurons, which can be used to detect neurotransmitter concentrations. If the electrode is thin enough, it can be inserted directly into a cell and used to detect concentrations of intracellular molecules, such as metabolites or even DNA.