This paper highlights the contribution of Leo Szilard in the development of atomic age. Szilard and his mentor Einstein were both theorists who shared a practical side. Szilard's work, included publication of a theory in statistical mechanics was recognized a generation later as a seminal paper in information theory. Szilard studied X-ray diffraction. He designed and filed patents for an electron microscope, as well as for a linear accelerator and a cyclotron, which became instruments for probing the structure of an atom. Development was dramatically escalated after the 1942 demonstration of a chain reaction. A chain reaction would require finding an element or isotope with a high probability of absorbing neutrons followed by the release of more free neutrons. The element subsequently would split to form smaller atoms. Szilard launched initiatives for the peaceful use of nuclear energy while trying to stop the arms race and prevent further use of nuclear weapons.