The International Space Station has been home to humans for more than 20 years.

The lab was launched in 1998 and received its first visitors two years later. NASA wants to keep the space station going for at least another 15 years.

Russia's space agency said Tuesday that it would pull out of the aging station after the current international arrangement ends in four years.

Russia's involvement may be ending, but the legacy of the International Space Station is still going strong.

The International Space Station has been in space for over two decades.

The landmark 'Twins Study,' which showed that living in space can change human DNA

A picture shows identical twin astronauts Mark and Scott Kelly.
Identical twin astronauts, Mark and Scott Kelly, took part in the "Twins Study."
NASA

Ahead of putting boots on the moon and Mars, a lot of research is being done at the International Space Station. NASA compared the health and biology of identical twins Mark and Scott Kelly.

Kelly's genes were found to have changed in space. After Scott's return to Earth, researchers discovered that his telomeres were longer than Mark's.

Experiments are being conducted on the International Space Station to fight bone and muscle loss. NASA says astronauts lose up to 2% of their bone density in space.

The first observation of an unusual 'cool-flame' 

An experiment abord the ISS shows the appearance of a 'steadily-burning cool flame'.
An experiment aboard the ISS shows the appearance of a steadily-burning "cool flame."
NASA

Scientists aboard the International Space Station were able to observe large fuel droplets extinguishing. The scientists observed low-temperature, soot-free flames in burning fuels for the first time after the initial burn.

According to NASA, the cool flame flickers at about 600 degrees Celsius. The temperature of a candle flame is about 1,400 degrees Celsius.

The scientists were able to see the flame in heptane fuel burn for the first time when they were aboard the International Space Station.

It's possible that the discovery will help scientists use fuel more efficiently in the future.

Astronauts send the first tweets from the ISS

The International Space Station updated to a better internet connection in 2010, allowing astronauts to use social media.

—TJ Creamer (@Astro_TJ) January 22, 2010

This isn't the first time an astronauts has sent a message from the International Space Station.

Access to the internet on the space station was limited until 2010 and that's when NASA sent a message to Mike Massimino. Massimino sent messages to the Mission Control Center on Earth.

The launch was great. The adventure of a lifetime has begun, and I am feeling great, working hard, and enjoying the magnificent views.

The ISS became one of the first space tourism destinations

Japanese billionaire Yusaku Maezawa floats inside the International Space Station.
Yusaku Maezawa, a Japanese billionaire, floats inside the International Space Station in this photo, uploaded on December 9, 2021, and obtained from social media.
Yusaku Maezawa/Instagram/Reuters

Dennis Tito, a US millionaire, was the first space tourist, spending eight days on the International Space Station.

In total, 14 people have gone to the space station as commercial spaceflight participants, including Cirque du Soleil founder Guy Laliberté, Russian film director, and actor, and billionaire Yusaku Maezawa.

Commercial space opportunities have been opened by NASA in the past. The first private mission to the International Space Station was launched by Axiom Space. "We are opening a new era in human spaceflight," Michael Lpez-Alegra, a former NASA astronaut who is also an Axiom executive and mission commander, told his followers. The initiative will bring working, living, and research in space to a much broader and more international audience.

Astronauts grew plants on the ISS and made space tacos

In order to help NASA study plant growth in low gravity, astronauts have grown fresh food on the space station in order to give them fresh grub. Three types of lettuce, radishes, and peas have been successfully harvest by the astronauts. Chili peppers grown in space were used to make the first space taco.

The astronauts are growing plants. The first flower to bloom in space was photographed by Scott Kelly.

A Russian film crew filmed the first fiction movie fully shot in space

In October of 2021, a Russian film crew went to the space station to shoot a full-length film. A doctor is sent to the station to treat a sick cosmonaut.

"I'm feeling a bit sad today," actress Yulia Peresild said on Russian state TV, after landing on Earth after 12 days of filming, according to CBS News. "It seemed that 12 days would be a lot, but I did not want to leave when everything was over."
yulia peresild adjusts spacesuit neck line headset
Actress Yulia Peresild attends her spacesuit check ahead of her expedition to the International Space Station, at the Baikonur Cosmodrome, Kazakhstan, on September 19, 2021.
Andrey Shelepin/GCTC/Roscosmos/Handout via Reuters

This is the first fiction production to be filmed in space. An eight-minute movie shot by space tourist Richard Garriot, called " Apogee of Fear," was filmed on the International Space Station.

An ongoing example of international cooperation in a divided world

View of an aurora taken from the International Space Station as it crossed over the southern Indian Ocean on September 17, 2011.
View of an aurora taken from the International Space Station as it crossed over the southern Indian Ocean, on September 17, 2011.
NASA

Since it's launch in 1998, the ISS has been an example of international collaboration. The station is made up of space agencies from the US, Europe, Canada, and Japan.

Hundreds of people from 20 countries have traveled to the International Space Station.

Russia's space agency decided to pull out of the International Space Station after 2024 due to the war in Ukraine, ending a long-standing partnership with NASA. NASA Administrator Bill Nelson said in a July 26 statement that the agency had not been notified of any plans to end cooperation with the International Space Station.

Nelson said that NASA is committed to the safe operation of the International Space Station through the year 2030. NASA has not been made aware of any decisions.

Dazzling views of Earth from space — including auroras and volcanic eruptions 

The city lights of Italy, including the French island of Corse and Italian islands of Sardinia and Sicily, are pictured from the International Space Station.
The city lights of Italy, including the French island of Corse and Italian islands of Sardinia and Sicily, from the International Space Station.
NASA

The International Space Station is 250 miles above the planet and has astronauts who travel at 17,500 mph. They frequently share beautiful images looking down at Earth, snapping shots of phenomena like the Aurora, volcanic eruptions, and light pollution. The term " the overview effect" was invented by Frank White in a 1987 book.