Early this morning, a NASA astronaut and a Russian cosmonaut ventured into the International Space Station’s newest room, the expandable BEAM unit, for its inaugural visit.

The habitat was both “pristine” and cold, the astronaut, Jeff Williams, told NASA after he opened the hatch for the first time shortly before 5 a.m. ET. He collected an air sample and data from the module, which was fully inflated on May 28. The space agency originally struggled to expand the innovative new module, running into trouble on May 26 when it didn’t inflate as planned.

Related: Watch NASA inflate a new room on the ISS Thursday

NASA said that astronauts will go into the new module Tuesday and Wednesday and will be sure to close the hatch when they're done.

Launched up to the space station on April 8, the approximately 3000-pound BEAM module was a little longer than 7 feet long before it was inflated to its full size of about 13 feet long. Made by Bigelow Aerospace, BEAM— which stands for Bigelow Expandable Activity Module—  will stay on the station for a two-year-long test, and later will be sent to burn up in the atmosphere.

Each year, crew members may go into BEAM about 6-7 times, NASA says, and will analyze variables like radiation exposure. 

Related: Astronaut headed to space station describes what she'll miss most on Earth

NASA is interested in expandable modules because they take up less space in a rocket and could possibly be used on a Mars mission. 

On June 24, the space agency will send astronaut Kate Rubins up to the ISS aboard a Soyuz spacecraft; the 37-year-old scientist will, among other research, look at how heart cells behave in a weightless environment.

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