Hundreds of schools around the UK have marked the Holocaust Memorial Day by hearing a survivor's story.
Rudi Oppenheimer was 12 when he and his family were sent to the Bergen-Belsen concentration camp by the Nazis.
They were kept in the camp as prisoners, and the Nazis deliberately made conditions so bad that people would die.
People were killed or allowed to starve, and Rudi's mum and dad were among those who died.
Now, 70 years later, Rudi works hard telling people about his experiences so that they will remember the Holocaust and try to make sure that nothing like it happens again.
This was the first time that his story was shared live online so that children around the country could all tune in to hear him speak.
It's important people like Rudi share their stories so that we can make sure nothing like this ever happens again.