She first drew attention in August 2018 when she skipped school to protest outside Swedish parliament each Friday.
The world joined
The teen activist was soon joined by a small group of other school strikers in Stockholm, before the campaign attracted tens of thousands of students in more than 24 countries, taking part in Friday school strikes around the world.
By March 2019, the number of students taking part in worldwide Friday demonstrations hit more than two million across 135 countries.
Nobel Peace Prize
The now 16-year-old has since been nominated for a Nobel Peace Prize, named one of the world's most influential people by Time magazine and appeared on its cover.
Thunberg has also been awarded the French Normandy Freedom Prize.
Humble start, big achievements
In less than a year since starting the "Fridays for Future" campaign, Thunberg has addressed the European Parliament, met Pope Francis and addressed the UK's House of Commons.
In August 2019, Thunberg sailed into New York Harbour on a zero-carbon emissions vessel, completing a nearly 14-day journey from England to take part in a United Nations climate summit.
Meanwhile, the total number of climate strikers reached 3.6 million people across 169 countries.
Never give up!
Teen climate champion Greta Thunberg brought her global environmental message to the heart of the US government on Friday, telling her legion of supporters outside the White House, "Never give up."