In this article, we offer a look inside our prototype compact X-ray tube by reporting on our findings when we experimentally studied it. We studied the prototype experimentally to characterize its primary components, i.e., carbon nanotube (CNT)-based cold cathode, electrostatic lens and transmission-type anode, and to validate our previous simulation studies. We characterized the CNT-based cold cathode by studying the relationship between the electron emission current and its control parameter, electron extraction voltage. This relationship, commonly known as the current-voltage characteristic, showed an exponential-like nature that is expected from the Fowler-Nordheim model for field emission. Next, we characterized the electrostatic lens by studying the effects of lens voltage on the focal spot size. Their relationship showed a “V” trend and corroborated that we can control the focal spot size by controlling the lens voltage. We then characterized the transmission-type anode of the prototype by studying its output X-ray energy spectra at different anode voltages. We could control the highest and the mean X-ray energies generated from the transmission-type anode using the anode voltage. For the same anode voltage and aluminum filtration, when we compared the Xray energy spectrum generated from the transmission-type anode with that of the conventional reflection-type anode, we observed that the two energy spectra agreed with each other.