Have you ever wondered how astronauts at the International Space Station (ISS) are keeping themselves clean in an extra-ordinary condition?

NASA astronaut Karen Nyberg showed a glimpse of how challenging it is to maintain proper personal hygiene under zero gravity in space through avideo posted in YouTube, which has now gone viral.

Nyberg, who is a member of the Expedition 36 onboard the ISS, showed the procedure of washing hair through a video titled "Inside the ISS - Hair Raising Hygiene" posted on the InsideISS YouTube channel. The video has almost 1.2 million views five days after it was uploaded.

"I've had a lot of people ask me how I wash my hair in space, and I thought I'd show you how I do it," Nyberg said.

Nyberg said that they are also using the same kind of things used on earth - water, shampoo, comb, and towel. It sounds normal at first, but the thrill began when the woman astronaut began squeezing water from a bag. It gets tricky as the water floated away, leaving her with no choice but to do the best she can to get the water back into her hair.

"Sometimes the water gets away from you. You try and catch as much as you can," Nyberg said.

After spreading water into her hair, Nyberg applied a no-rinse shampoo. However, she added that using shampoo is not enough to get her hair cleaned.

Nyberg said that without running water, the towel is used to get the dirt out of her hair. And once her hair reaches the "squeaky clean" status, she will let her hair dry naturally as water eventually evaporates and becomes humidity inside the space station, which in turn will become their source of drinking water.

"As the water evaporates from my hair, it'll become humidity in the air. Then our air-conditioning system will collect it into condensate, and our water processing system will turn it into drinking water," Nyberg said.

The "Hair Raising Hygiene" video is the latest instructional astronaut videos that have gone viral. A previous YouTube video titled "How To Wash Your Hands In Space" already has more than 3.2 million views, while the "Tears In Space" uploaded by the Canadian Space Agency already got more than 2.6 million hits.