The aim of this video is the study of the X-ray. That means the analysis of the X-ray intensity, produced through “Bremsstrahlung” (braking radiation) by a material for each wavelength. It begins with the historical development that led to the discovery of X-rays and the knowledge of their electromagnetic nature. Then it explains in detail the experimental setup that allows the measurement of the X-ray spectrum and analyses the physical processes that give rise to it, ending by commenting on some current applications of X-rays.