Thousands of students in more than 1,000 cities around the world are skipping school in protest against their governments' failure to act on global warming.
The coordinated 'school strike' was inspired by 16-year-old Swedish activist Greta Thunberg, who began holding solitary demonstrations outside the Swedish parliament last year.
Since then, the protests have snowballed and Friday's global rallies are thought to make up one of the biggest ever coordinated international actions against climate change.
Ms Thunberg's protest in Sweden sparked a chain reaction around the world, with thousands of schoolchildren following her lead in February and skipping school, in protests that drew both admiration and criticism.
Friday's protests are taking place in about 100 countries, from New Zealand to the United States.
Scientists have backed the protests, with thousands signing petitions in support of the students in Britain, Finland and Germany.
Here are the some of the best photographs from the worldwide protests: