I managed to see this, uninterrupted, on PBS. Superb documentary that everyone deserves to see.
I was born shortly after the two nuclear bombs were dropped on Japan, deemed then to be a necessary evil to get Japan to surrender. In the 1950s I remember the drills school children had to do in the event of a nuclear attack from the USSR. So "the bomb" and all it implies has been with me my whole life. Those born after about 1960 really have only a vague idea.
The idea for a nuclear bomb came when scientists examined some fission products and, using Einstein's energy-mass formula, realized how much energy release could occur. WW2 was not going well and a large, secretive operation in very remote location amassed all the best minds to design and build nuclear bombs.
This documentary covers all that in its first half, and includes many interviews with some of the project's scientists. And it includes footage of the bombing in Japan and the aftermath.
The second half covers the ensuing nuclear bomb manufacture and testing through the 1950s and 1960s. Mostly the U.S. and the Soviets "one-upping" each other in a Cold War. And the inevitable understanding that no one wins in an all-out nuclear war. It really is man's creation which can destroy all humanity.
Really, every person over the age of 17 or so should see this documentary.