The Hillsborough disaster was one of the worst sporting tragedies in British history.
On 15 April 1989, 96 Liverpool football fans were killed by a crush at the Sheffield Wednesday stadium, during an FA Cup semi-final.
There was a big investigation at the time - but not all the details were made public by the government.
Now, MPs will debate whether to release thousands of documents about the investigation.
Ore examines the history behind the disaster.