Ernst Lawrence was an American nuclear scientist who won the Nobel Prize in Physics in 1939 for his invention of the cyclotron. Although he started his college education with chemistry he soon changed to physics and ultimately earned his PhD in physics from the University of Yale. While working as an associate professor at the University of California, 28 year old Lawrence developed a circular particle accelerator, later termed cyclotron. The invention, not only earned him Nobel Prize, but also the full professorship at the age of 29 and directorship at the Radiation Laboratory at 35. Although he received the patent for his new invention, he never accepted any royalty from it. Instead, he concentrated on developing larger and more powerful cyclotrons and helped others to build them. Once the World War II started, he got involved in number of defense projects. He was inducted into the Manhattan Project, and the Uranium-235 required for making the Hiroshima bomb came mostly from his laboratory at Berkeley. He also advocated strongly for manufacturing the Hydrogen bomb. At the same time, he was equally interested in developing nuclear medicine and collaborated with this brother in this.