Greta Thunberg is an 18-year-old activist from Sweden.
She has become one of the world's best known climate campaigners.
Three moments that made Greta Thunberg a global figure
1. School strikes
Thunberg started protesting outside the Swedish parliament in 2018, when she was 15.
She held a sign saying "School Strike for Climate", to pressure the government to meet carbon emissions targets.
Her small campaign had a global effect, inspiring thousands of young people across the world to organise their own strikes.
By December 2018, more than 20,000 students - from the UK to Japan - had joined her by skipping school to protest.
A year later, she received the first of three Nobel Peace Prize nominations for climate activism.
2. Challenging world leaders at the United Nations
In 2019, Thunberg sailed across the Atlantic on a yacht to attend a UN climate conference in New York.
Delivering what is probably her most famous speech, she angrily told world leaders they were not doing enough.
"You all come to us young people for hope. How dare you? You have stolen my dreams and my childhood with your empty words," she said.
How dare you? You have stolen my dreams and my childhood with your empty words.
3. Sparring with Trump and Putin
Thunberg was named Time Magazine's Person of the Year in December 2019.
Her growing fame caught the attention of world leaders, not all of them supportive.
Donald Trump, who was US president at the time, tweeted that she should "work on her anger management problem" and go to "a good old fashioned movie with a friend".
Thunberg then changed her Twitter bio to: "A teenager working on her anger management problem."
She changed it again to quote Russian President Vladimir Putin's description of her as a "kind but poorly informed teenager".
The following year, she told the World Economic Forum in Davos the world should be "scared" by Mr Trump's decision to leave the Paris accord - an international agreement setting countries' emissions targets.
What are Greta Thunberg's aims?
She wants people in power across the world to act with more urgency in tackling harmful emissions.
For example, she called EU plans to reduce harmful emissions by 2050 a "surrender".
Thunberg said: "We don't just need goals for just 2030 or 2050. We, above all, need them for 2020 and every following month and year to come."
In 2021 she opposed the construction of the UK's first deep coal mine in 30 years.
However, Thunberg has avoided getting into the detail of what action should be taken, saying "it is nothing to do with me".
What do people say about her?
Thunberg has received support from climate activists, scientists, world leaders and the Pope, who told her to continue her work.
Broadcaster and naturalist Sir David Attenborough told her she has achieved things many others have failed to do, adding: "You have aroused the world. I'm very grateful to you."
Prince Harry praised Thunberg's campaigning, saying "every country, every community, every school, every friendship group, every family needs their own Greta".
Former presidential candidate Hilary Clinton thanked her for "her willingness to tell hard, motivating truths", while celebrity Kim Kardashian has said Thunberg is "brave and courageous".
She’s the only friend I’d skip school for. pic.twitter.com/uP0vwF2U3K— Malala (@Malala) February 25, 2020
How does she live her life?
Thunberg has said she has stopped buying clothes and does not fly.
But she said she wasn't "telling anyone else what to do".
In 2019 she told chat-show host Ellen she was vegan.
In June 2020, Thunberg told the BBC that she had been catching up on her school studies during the pandemic.
She has Asperger syndrome, a developmental disorder, and has described it as a gift. She said being different can be a "superpower".
What about her family?
Thunberg's mother, Malena Ernman, is an opera singer and former Eurovision Song Contest participant.
Her father Svante Thunberg, is an actor and a descendant of the scientist who created a model of the greenhouse effect.
He initially opposed his daughter's decision to be on the "front line" of the battle against climate change.
He worried about Greta putting herself "out there with all the hate on social media".
The elder of two girls, she says she learned about climate change when she was eight.