On 16 June 1976 an incident happened in South Africa that made headlines around the world that has since become known as the Soweto uprising.
On that day a protest by black African children in the country ended when police fired guns at them. The government said 95 people - some of them children - were killed. It's thought more than 500 people died.
At the time the South African government had a law called apartheid, which meant black people had fewer rights than white people and had to live separate lives from them.
So what happened on that day, and what did it mean for South Africa?
How did apartheid start?
In 1948 a new government started introducing laws that made the lives of black people and white people very different.
They were not allowed to get married to each other, had to use different hospitals, buses, schools and couldn't even use the same beaches.
But worse than these were something called pass laws, which were introduced in 1958.
They stopped black people from living or working in towns unless they had the right papers. That meant they had to live and stay in very poor areas until they were needed for a job.
Black people were very angry about this, and there were lots of protests, but nothing changed until apartheid ended many years later.
How did the Soweto uprising start?
In 1976 the government in South Africa decided that black schools could only teach in a language called Afrikaans.
This language was used by the white people and the government in South Africa.
After years of apartheid this change was more than the black people could take, so they took action.
At 7am on 16 June thousands of schoolchildren started to protest against the new law, singing songs and waving signs.
At first police used gas to try and calm things down, but then started firing guns. The children protesting threw stones back at the police.
The protest turned into a riot which lasted three days and adults joined in.
What happened after the uprising?
The uprising and the way it was dealt with brought the problems in South Africa to the world's attention.
Some countries introduced things called sanctions against South Africa, which meant they refused to sell goods to the country or buy goods from it.
Other countries also refused to play South Africa at international sport.
Apartheid eventually ended in 1990.