Greta Thunberg is leading kids and adults from 150 countries in a massive Friday climate strike.

Young people from around the world are leading a massive coordinated strike from school on Friday, September 20, to protest government and business inaction on climate change. It is likely to be one of the largest environmental protests in history.

The Global Climate Strike comes just before countries will gather at the United Nations for the Climate Action Summit on September 23, where countries are supposed to ramp up their ambitions to curb greenhouse gases under the 2015 Paris climate agreement. A second worldwide strike is planned for September 27.

“If you can’t be in the strike, then, of course, you don’t have to,” 16-year-old Swedish climate activist Greta Thunberg, the original school striker who last year began demanding more action from her government on climate change with weekly protests, told Teen Vogue. “But I think if there is one day you should join, this is the day.”

Thunberg has become an increasingly influential figurehead and voice for youth climate angst and activism. Since she no longer flies because of the aviation industry’s high carbon emissions, she was offered the opportunity to travel to the US on a zero-emissions sailboat. This week, she’s been in Washington, DC, speaking before Congress and meeting with US lawmakers, including House Speaker Nancy Pelosi (D-CA), before heading to New York City for the strikes and the summit.