Scientists will very shortly be sending some slime into space so that astronauts can learn more about how a non-water fluid behaves in microgravity. Newsround has had a look at what other strange items have been sent out of this world!
Scientists will very shortly be sending some slime to the International Space Station on board SpaceX's Falcon 9 rocket! It was due to go yesterday, but unfavourable weather meant that lift-off needed to be delayed. Once the slime has reached the ISS, astronauts aboard the station will play games with it, toss slime-filled balloons, make slime bubbles and even spray each other with slime in order to understand how a fluid, which isn't water, behaves in microgravity. The rocket will also be taking over 5,000 pounds of supplies for the astronauts aboard the station.
A car isn't the type of transport you'd think of in space but tech personality Elon Musk launched one of his own sports cars into space! Sent up above the atmosphere onboard the Falcon Heavy's first test flight, Mr Musk didn't want to risk sending something important on the world's most powerful rocket - instead Elon decided his old red Tesla roadster with a mannequin, dressed in a space-suit, strapped in the driver's seat could make the journey! Since the test flight, lots of other things have been successfully sent to space on the Falcon rockets.
Movie prop: Luke Skywalker's lightsaber was sent to space in 2007, it travelled on the Discovery shuttlecraft and marked the 30th anniversary of the original Star Wars film in 1977. The Force was with the shuttlecraft crew, obviously.
Food: Edible delights being sent into space has been a popular idea - and a way to study the effects of space. Amongst the strangest is this pattie and chips sent in 2017 by a chip shop in Hull, England. It was attached to a weather balloon to make its journey up and was studied by local schoolchildren!
Satellites: This giant satellite, that looks a bit like a disco ball, is called the Humanity Star. It was sent into space in January 2018 and spent several months up there before re-entering the Earth's atmosphere. The company behind it says the Humanity Star is a "reminder to all on Earth about our fragile place in the universe", and will "create a shared experience for everyone on the planet".
Toys: In 2011, when Nasa launched its Juno spacecraft on a mission to learn about the planet Jupiter, they included three Lego figures on board! They hoped getting the toys involved would inspire more children to be interested in science and technology. But these aren't the only toys to head into space - a Buzz Lightyear figure from the film Toy Story spent 450 days in space too!
Animals: In the early days of space exploration, nobody knew if people could make the journey from Earth to space, and back, safely, so they used animals to find out. In 1961, Ham became the first chimpanzee in space and successfully returned to Earth. Scientists found that Ham was slightly tired after the flight, but in good shape.
Sounds: Recordings of various sounds have been sent up to space in the hope that aliens or other life forms will hear the noises. The sounds have included a shepherd herding his sheep, rainfall, a heartbeat, thunder and someone sawing wood.