The history of quantum electronics is considered in relation to Einstein's theory of radiation. It is shown that the papers of Albert Einstein on the quantum theory of radiation, published between 1905 and 1925, established the physical basis of quantum electronics. A discussion of quantum electronics devices and applications demonstrates, that irrespective of the wavelength (radio frequencies, microwaves, infrared, visible, ultraviolet, etc.), Einstein's theory of radiation is the cornerstone of quantum electronics as a whole.