NASA astronauts Christina Koch and エロ 映画Jessica Meir made history on Friday, embarking upon the first ever all-female spacewalk. Finally.

Residents of the International Space Station, the pair ventured outside the ISS to replace a power controller that failed during the weekend prior.

Although there have been a total of 221 spacewalks performed to maintain the space station, it's the first ever conducted by two women. These two, in fact:

It's been a long time coming. Koch, who now has four spacewalks under her belt, had already been scheduled to take part in the first all-female spacewalk in March, when she and astronaut Anne McClain were scheduled to venture outside the ISS to replace older, nickel-hydrogen batteries, with lithium-ion versions.

Plans were scrapped, however, as there was only one suit available in the size required by both women. Yeah, it did not go down well back on Earth.

But on Friday morning, it finally happened.

Livestreamed by NASA, the pair exited the Quest airlock and ventured to the far side of the ISS on the Port 6 truss structure. Koch was wearing the spacesuit with the red stripes, while Meir was wearing the suit with no stripes. Notably, it was Meir's first ever spacewalk.

Excitement was high as the pair did last-minute checks of their suits and equipment with help from Mission Control's Stephanie Wilson before the hatch opened, and the official spacewalk began when the suits switched over to battery power at 7:38 a.m. ET.

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The objective was to replace a faulty power unit, called a Battery Charge/Discharge Unit (BCDU). These regulate the amount of charge allowed into the station's batteries collecting solar energy. The BCDU, which has been working away since Dec. 2000, will head back to Earth on the next SpaceX Dragon resupply ship.

The ISS is powered by four sets of batteries and solar arrays, and while the failed unit, according to NASA, "has no impact on the crew’s safety or ongoing laboratory experiments," it does prevent a recently installed lithium-ion battery from adding to the station's power supply.

As significant a milestone as this is, perhaps it marks a step toward events like this being less exciting, more normal. Astronaut Tracy Caldwell Dyson, who has completed three spacewalks, noted this during NASA's commentary of the spacewalk.

"As much as it's worth celebrating the first spacewalk with an all-female team, I think many of us are looking forward to it just being normal," she said. "I think if it signifies anything it it is to honor the women who came before us, who were skilled and qualified and didn't get the same opportunities that we have today because it is so normal."

Koch, for one, is not done making history at the ISS. She's gearing up to break the record for the longest single spaceflight by a woman on Dec. 28, taking over the record of 288 days set by former NASA astronaut Peggy Whitson in 2016-17.

What a day.

The spacewalk can take between five and six hours, so Mashable will update this post with developments as they happen.