What does the modern idiom “open Pandora’s box” mean?

The modern idiom “open Pandora’s box” means to start many unforeseen problems.

English speakers use the expression when an action or decision produces a complicated chain of troubles that is difficult to control or reverse. The phrase draws on the myth in which opening Pandora’s container releases numerous evils into the human world.

The idiom does not usually refer to a literal container. It is a metaphor for unintended consequences, especially when a seemingly small step exposes a much larger set of difficulties. News reports, political commentary, law, technology, and everyday conversation all use it in this figurative sense.

The expression is sometimes confused with “skeletons in the closet,” which concerns hidden secrets, or “a can of worms,” which also means creating complications. Pandora’s box specifically emphasizes consequences that multiply after an initial opening or disclosure.