A group of school children in Merseyside have been getting a lesson they are unlikely to forget - in a replica prison.
It sounds scary but it's hoped a view of life behind bars will put young people off committing crimes when they get older.
Ricky's been to check it out.
"In the UK there are more than 80,000 men and women serving time in prison for committing serious crimes.
Prisons are well known for being miserable places and some of the people who end up there might never be released.
What's prison like?
It's not somewhere you want to spend a lot of time, but Newsround sent me to jail to see what it's really like.
But the prison I visited is mobile, it's based inside a truck and thankfully it's not real.
A group of former criminals from Liverpool, including Bob Croxton, raised money to create a replica of a prison cell.
It was built inside an 18-tonne lorry and it's hitting the streets of Liverpool in a bid to show children the harsh realities of jail. They hope it will stop kids from getting locked up when they're older.
I've never been inside a real prison before. I've seen them on shows like EastEnders and Neighbours, but never in real life. So stepping into the replica cell was an interesting experience.
The room is really small, I felt extremely claustrophobic.
It contains a bunk bed, toilet, sink, and a table and chair. There are no computers, no sofas and no luxuries whatsoever.
The iron bars are dark and dingy and the mattress had a plastic coating.
Kids get a chance to walk in and listen to stories from reformed criminals who have actually spent a lot of time inside a real jail.
The whole experience is quite realistic, children are searched by prison wardens and mustn't talk unless they're spoken to.
I was relieved to leave the prison cell after just a couple of minutes and so were the school kids.
One of the young girls found it a bit too much and got pretty emotional. She said the experience opened up her eyes to see just how difficult life on the inside is.
Bob Croxton who came up with the idea said: "Our ultimate aim is to prevent tomorrow's potential offenders from taking that path. Young people can't understand what life is like in prison until they're locked up behind bars."
The cells will be hitting the streets of Liverpool at the end of September. "