The American criminal justice system consists of 2.2 million people behind bars, plus tens of millions of family members, corrections and police officers, parolees, victims of crime, judges, prosecutors and defenders.

Tens of thousands of people every year are packed into vans run by for-profit companies with almost no oversight.

Imagine living in a cell that’s smaller than a parking space — with a homicidal roommate.

You are about to enter Philadelphia’s largest jail. Here is what you should know.