Take a look inside the station's new expandable module with astronaut Jeff Williams

BEAM, the International Space Station's new expandable habitat module, is open for business.

Astronaut Jeff Williams and cosmonaut Oleg Skripochka entered the module at 4:47 a.m. EDT (9:47 UTC) this morning. This marks the first time humans have ever been inside an expandable space module—a technology that could have far-reaching implications for trips to deep space.

Here's a video from NASA's Johnson Space Center showing the initial ingress:

Williams and Skripochka wore face masks as they entered, which is standard procedure for initial inspections of cargo ships visiting the station. The duo collected an air sample, exited, and then re-entered to start gathering sensor data that was captured during the module's expansion on May 26 and 28.

Williams told ground controllers it was cold inside, and the temperature at the aft bulkhead read 44 degrees Farenheit, which was in line with pre-flight simulations.

The crew is finished working inside BEAM for the day. They have opportunities to reenter on Tuesday and Wednesday to deploy more sensors.

BEAM was expanded after a seven-hour, marathon work session back on May 28. It will remain aboard the station for two years. Astronauts will enter the module from time to time to collect data samples, but for the majority of time the hatch will remain closed.