In the topic of cold field emission warrants special attention due to its extreme importance from the perspective of basic science, and at the same time, it has several applications in various advanced fields of prime importance. The quantum–mechanical aspects of tunneling, insulating emitter with negative electron affinity, the concept of field concentration, and hence the emission of an electron at applied energy far lesser than the work function of the material are instead a true wonder of basic science, and this is the reason the exact mathematical formulation of the phenomena is still in a stage of gradual development.