It is said to be the nation's longest building -- the nearly 2-mile-long Stanford Linear Accelerator Center, a government lab run by Stanford in Menlo Park.
It helped find the missing piece of the Big Bang Theory.
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It unlocked the earliest writings of Archimedes, hiding beneath layers of other writing and paint. A researcher from SLAC said it was written 2,200 years ago and again 30 years ago.
Now, that very same x-ray, in a donut-shaped part of the lab called the Synchrotron, is helping scientists learn about something else -- batteries.
"We can shoot through the full battery cell to see the battery in reaction in real conditions," SLAC associate staff scientist Yijin Liu said.
Watching the molecules as they charge and discharge is a game-changer for battery makers.
"They were almost guessing as to what was actually happening. They would develop a new battery pack, a new cell, with new materials, and it worked or it didn't," CalCharge President Jeff Anderson said.
That's why those companies are now teaming up with the national labs in a project called CalCharge.
It gives battery makers easy access to the government's tools and scientists to speed up innovation.
"You will see, hopefully, cheaper batteries for electric cars, things that have a longer range, cheaper batteries for the grid, and hopefully that means you'll end up getting a better iPhone battery at the end of the day," Lawrence Berkeley Lab staff scientist Venkat Srinivasan said.
Batteries have hit a plateau. While computer chips have doubled in density every two years, batteries have inched along, getting about five percent better per year.
Speeding that up could speed the adoption of electric cars.
"Which are important in the national interest for environmental reasons, for economic and energy security reasons," SLAC Strategic Planning Director Mark Hartney said.
There's one more way all this research serves the American public. Beyond just building better batteries for technology, another goal of it is learning how to build those batteries in America.
"We don't make batteries in the U.S. We've lost manufacturing a long time ago, so we think one of the opportunities in front of us is we can bring back U.S. manufacturing," Srinivasan said.
In fact, about half of the CalCharge companies are Bay Area startups and thanks to these x-rays, they won't be poking around in the dark.
"It takes the guesswork out of innovation," Anderson said.