Nuclear bombs are catastrophic weapons of mass destruction that have the ability to instantly destroy huge cities and kill thousands of people.
Although these weapons have been tested more than 2,000 times by nuclear powers like the United States and the Soviet Union/Russia, they have only been used in combat twice.
Tens of thousands of people died immediately when the U.S. detonated atomic bombs on the Japanese cities of Hiroshima and Nagasaki toward the end of the war.
In Los Alamos, New Mexico, the first atomic weapon was created as part of the Manhattan Project, a research project conducted by the American government from 1942 to 1945.
Before the Nazis could create a bomb, Einstein addressed a letter to the president requesting the US to start researching atomic weapons.
After receiving Einstein's letter, the American government started looking into whether nuclear fission could be used for military purposes.
The United States' work on developing the atomic bomb was a nationwide collaboration involving both commercial and academic institutions.
The top-secret Manhattan Project had the highest priority of all wartime undertakings from the U.S. government as the second world war progressed.
Scientists from both Canada and the United Kingdom subsequently joined forces on the project, and they both moved to the USA to assist out.
Theoretical research into the bomb's development, based on numerous experiments carried out around the nation, dominated until 1943
The bomb was set out on July 6 of that year in the barren Alamogordo Bombing Range, roughly 210 miles south of Los Alamos
The Manhattan Project's bombs that were dropped on Hiroshima and Nagasaki in August 1945 completely destroyed the cities and their inhabitants.