In 1969, US astronaut Russell Schweickart peed into a plastic receptacle while on the Apollo 9 mission.
The condom-like vessel allowed Schweickart - and the other crew members - to relieve themselves in space.
But they often made a big mess when they removed the receptacle - painfully, they learnt that size does actually matter. The astronauts would reach for the largest of the three receptacles, when perhaps a smaller one was sufficient.
"You only make that mistake once," Schweickart said after his return.
Since then, going to the toilet in space has become easier.
Modern space toilets even allow astronauts a brief, intimate timeout. But personal hygiene remains one of the greatest challenges onboard the International Space Station (ISS).
German astronaut Reinhold Ewald, who stayed at the space station MIR, told DW he was often pushed to the edge of his own limits. "It's not for the highly sensitive," he said.
Astronauts have to belt themselves down to the space toilet. Strong sucking pressure allows them to relax on the throne, despite the zero gravity. For missions outside of the craft, diapers can be used.
Water resources onboard the ISS are strictly limited, and transport costs are - well, astronomical. So water is recycled from urine.
"On the space station, even evaporated sweat and shower water are reused," says Rupert Gerzer, a health expert with the German Aerospace Center (DLR).
Excrement is shrink-wrapped and put out with the trash when it's full. Which, on a Soyuz capsule, means being shot out into orbit around the Earth.
The greatest hygienic challenge is the constant presence of moisture, says Gerzer: "Microorganisms and fungus can grow faster on a space station than on Earth."
To combat this, regular air and swipe samples are taken for early detection of potential infestations.
And there are no lengthy, hot showers in space. Astronauts have to make do with a few drops of water rubbed over their bodies or into their hair.
"It's more like a catlick," says Ewald.
Other than that, they can use moist, travel wipes.
Scarce resources also mean no water for washing clothes.
So, clothing gets thrown out after use.
"That means in space, you wear your undergarments an extra day," says Ewald.
Then there's the slow bodily deterioration astronauts experience in zero gravity.
Ewald recalls how this can slow the healing process: "I had a pimple on my forehead that just wouldn't go away."
Very serious illnesses rarely break out in space. But Gerzer says despite the lower risk of infection, "When it happens, it's much harder to react."
A hot shower is a highlight for astronauts when they return to Earth.
Ewald went so far as to allow himself the luxury of a bath after returning from MIR.
"Even though my heart felt somewhat fluttery, it was an amazing feeling."