The US government detonated hundreds upon hundreds of above-ground nuclear explosions from 1945 to 1963 — right up until the first nuclear test-ban treaty was signed.

The experiments tried out new bomb designs, measured their explosive power (called yield), verified that existing weapons still worked, and studied what might happen to anything and anyone unfortunate enough to be a target.

About 10,000 videos of such tests were filmed, analyzed, and locked away in high-security vaults, where they were nearly forgotten and began to decay.

More than five decades later, however, a team of scientists at Lawrence Livermore National Laboratory (LLNL) is working feverishly to rescue, scan, and reanalyze the high-speed films.

"This is it. We got to this project just in time," Greg Spriggs, a nuclear-weapons physicist at LLNL, said in a video about the digitization effort. "We know that these films are on the brink of decomposing, to the point where they will become useless."

Over the past five years, Spriggs' team has scanned some 6,500 films and reanalyzed them with modern digital tools for national security purposes. But as part of that work, the project has also declassified nearly 4,400 of the never-before-seen videos and uploaded about 500 of the clips to YouTube as of July 5, 2018. An additional 500 should go online within the next two years, after which the project will end, a LLNL spokesperson told Business Insider.

"These films are priceless to us," Spriggs previously told Business Insider.

Here are some of the videos recorded in the remote deserts of Nevada and over the Pacific Ocean, with descriptions of what they show.

This post has been updated with new information and video content. It was originally published on March 16, 2017.