Again, this is a part of Greek mythology. Pandora was the first woman on Earth (again, do these story-creators find anyone other than women???). She was given a jar and was asked NOT TO OPEN it under any circumstance. It's believed Pandora's box (jar) contained all the evils of the world. As usual, out of curiosity, she opened the box... all the evils were released. But she quickly closed the box - trapping the last one - HOPE inside the box. So if, someone talks about the Pandora's box it means - a process once begun/ or something once done that only generates more complicated problems further.