Ever since she learned about climate change, Greta Thunberg couldn’t understand why politicians weren’t treating it as an emergency. In August 2018, temperatures in Sweden reached record highs, fires raged across the country, and fifteen-year-old Greta decided to stop waiting for political leaders to take action. Instead of going to school on Friday, she made a sign and went on strike in front of Stockholm’s parliament building. Greta’s solo protest grew into the global Fridays for Future—or School Strike 4 Climate—movement, which millions have now joined. She has spoken at COP24 (the UN summit on climate change) and has been nominated for the Nobel Peace Prize. This timely, unofficial biography is her story, but also that of many others around the world willing to fight against the indifference of the powerful for a better future.