Since the time of Trinity -- the first nuclear explosion in 1945 -- nearly 2,000 nuclear tests have been performed, with the majority taking place during the 1960s and 1970s. When the technology was new, tests were frequent and often spectacular, and led to the development of newer, more deadly weapons. But starting in the 1990s, there have been efforts to limit the future testing of nuclear weapons, including a U.S. moratorium and a U.N. comprehensive test ban treaty. As a result, testing has slowed -- though not halted -- and there are questions about the future. Who will take over for those experienced engineers who are now near retirement, and should we act as stewards with our enormous stockpiles of nuclear weapons? Gathered here are images from the first 30 years of nuclear testing. Operation Greenhouse took place in the spring of 1951, consisting of four explosions at the Pacific Proving Grounds in the Pacific Ocean. This photo is from the third test, George, on May 9, 1951, the first thermonuclear bomb test, yielding 225 kilotons. A photo of a nuclear bomb detonated by the French government at the Mururoa atoll, French Polynesia. Upshot-Knothole Grable, a test carried out by the U.S. military in Nevada on May 25, 1953. A 280mm nuclear shell was fired 10km into the desert by the M65 Atomic Cannon, detonating in the air, about 500 feet above the ground, with a resulting 15 kiloton explosion.