Do you speak about Greta Thunberg to your kids? I do. In 2018, when most teenagers are spending their time on the mobile devices, 15-year-old Greta Thunberg started a school strike in Sweden to draw attention to the climate crisis and it’s astonishing when it comes from a child.

“We are children saying, ‘Why should we care about our future when no one else is doing that? And why should we bother to learn facts when facts don’t matter in this society?’ When children say something like that, I think adults feel very bad,” Thunberg told TIME in April.

Greta just completed a transatlantic journey by sailboat and is scheduled to speak at the United Nations General Assembly’s Climate Action Summit. She is taking another chance to talk about the urgent necessity of international action on the climate crisis. And this girl is frank, even with world leaders.

In late August, she landed in the U.S. after a 15-day boat trip across the Atlantic, and she has plans for a months-long tour of the Americas—with a zero-carbon footprint. “This is an existential crisis that is going to affect our whole civilization, the biggest crisis humanity has ever faced,” she says. “I’m not planning to stop this movement, and I don’t think anyone else is either.”