Boldly going where no one has gone before, NASA's getting a look inside the first pop-up portable expansion to the International Space Station.

FOX's Dave Anthony reports:

They're exploring their new space in space:

(NASA) "Houston, we're ready for BEAM inflation."

That was last month when astronauts began inflating beam. The Bigelow Expandable Activity Module.

On Monday, Jeffrey Wlliams floated inside for the first time, saying it's dark and cold. But there's no evidence of any condensation. They'll install sensors and other gear this week.

The attachment to the International Space Station is 13-feet-long, about ten feet in diameter, but it's only there for two years of tests. BEAM will remain closed off. Entered once every few months to collect temperature pressure and radiation data.

The goal is to see how such an inflatable chamber withstands outer space.

Dave Anthony, FOX News.