Our wonderful universe is made up of two main types of stuff. Matter, which is made up of atoms and molecules and radiation energy, which rapidly travel from one place to another till it, dissipates. Matter and energy are inter-convertible; Professor Albert Einstein taught this fact for the first time. The basic understanding of the atomic structure and the tube design helps the dental surgeon in the understanding the various properties of X-rays emanating from the tube and how to take good care of the X-ray unit.