Twenty years ago today, a crew of three American and Russian astronauts cracked open a heavy steel hatch and climbed aboard the International Space Station.
And space exploration was never the same again.
Since then, the football field-sized structure – the brightest object in the sky after the Sun and Moon – has been continuously occupied by a multi-faith and multinational crew of scientists and engineers.
On November 2, 2000, Nasa astronaut Bill Shepherd and two Russian cosmonauts Yuri Gidzenko and Sergei Krikalev arrived. A handful of astronauts had been there before to build the modules, but this was the first resident crew.
Since then, 240 people from 19 countries have visited the station. This includes the first woman, Nasa astronaut Susan Helms in 2001, and the first Arab astronaut Hazza Al Mansouri in 2019.
But there are many memorable moments that have taken place on ISS. Here we look at five of the most memorable.
First space tourist - and a $20 million cheque
Space tourism may be a hot topic now, but the idea was born two decades ago when a private citizen paid to go to space.
American multimillionaire Dennis Tito became the world’s first space tourist on April 28, 2001.
It is said he paid about $20 million to spend eight days on the ISS after the Russians arranged the trip. Nasa refused to take him as he wasn’t a trained astronaut.
Mr Tito was 60-years-old at the time and going to space was his lifelong dream.
Since then, about seven similar trips have been arranged for private citizens and astronauts from countries that are not ISS-partners.
SpaceX billionaire Elon Musk and Virgin Galactic hope to make regular space tourism flights a reality, including trips to the Moon, ISS and sub-orbital flights.
Space station's first birth
On November 30, 2009, butterflies were born on the station.
Two types emerged from their cocoons inside a genetic bioprocessing container.
Seven cocoons were taken to space as part of an educational experiment for scientists, pupils and teachers. The butterflies’ birth and growth under microgravity conditions were studied.
They were the first Monarch butterflies in space and the first Painted Lady butterflies to go through all phases of development in microgravity.
Scientists found that the Monarchs’ lifespan on Earth is about two weeks, but they lasted four days in space because of the tight space. It took 15-minutes instead of three to six minutes for them to dry after coming out of their cocoon.
The Painted Lady lives for up to two weeks on Earth, but were alive for about a week in orbit.
Growing the first vegetables
Red romaine lettuce was the first vegetable to been grown in space, in August 2015 and they were a tastier alternative than the odd packaged space food astronauts have to eat.
But, they were grown mainly to study how plants and vegetables can be grown in microgravity and provide astronauts with a sustainable food source in future.
The astronauts ate half of the batch - and the rest were brought back to Earth.
Since then, astronauts have grown three types of lettuce, Chinese cabbage, mizuna mustard, red Russian kale and zinnia flowers.
They are all grown in the Advanced Plant Habitat, a growth chamber on the station used for plant research.
It uses LED lights and a controlled release fertiliser to deliver water, nutrients and oxygen to the plant roots.
The chamber also has cameras and more than 180 sensors, so the ground control team can monitor growth.
Astronauts growing their own food resources is vital to meet goals of establishing a human base on other planets or the Moon.
Running a marathon in space
Two to three hours of exercise daily is required for astronauts to maintain their health, but one astronaut took his workout to another level.
In 2016, British astronaut Tim Peake completed the fastest marathon in space. He gained a Guinness World Record for his efforts, finishing in three hours, 35-minutes and 21-seconds for the London Marathon.
The accomplishment came nine years after Nasa astronaut Sunita Williams ran a marathon in space for the Boston Marathon.
Both of them ran for hours on the space station’s treadmill.
First live Arabic-language tour of the ISS
Tours of the space station have been done in many languages – English, Russian, French, Italian and others.
But, it was only last year when the first Arabic-language tour was done by Emirati astronaut Hazza Al Mansouri.
The 36-year-old was the first Arab on the space station and went there for eight days.
The full video of his tour was released more than a month after he landed back on Earth.
Five more facts about ISS:
- ISS can accommodate three to six astronauts comfortably, but it has held nine people at times - and once 13 during a crew changeover in 2009.
- It travels fast, orbiting Earth 16 times in 24 hours
- The station is often visible to humans on Earth because of its large solar panels
- Astronauts have carried out more than 230 spacewalks, often to repair parts of the station
- In 2019, Nasa astronaut Anne McClain was the first person accused of committing a crime in space, when her estranged spouse, Summer Worden, accused her of accessing a bank account without permission. It was later found to be a false claim