What modern expression means an action that creates many unexpected problems, like Pandora’s story?

“Opening Pandora’s box” means taking an action that creates many unexpected problems. The expression comes from the Greek myth in which Pandora’s opened container releases troubles into the human world.

In modern English, the phrase is usually metaphorical rather than literal. Someone may say that a decision “opened Pandora’s box” when it produces consequences that are difficult to control or reverse. The expression is often used in journalism, politics, law, science, and everyday conversation.

The wording is based on the later English tradition of calling Pandora’s pithos a box. The ancient source does not present the exact modern idiom, and the phrase does not necessarily imply deliberate wrongdoing. Its core idea is the sudden release of numerous complications from a single action.