“Pandora’s box” is the modern English expression for a source of unexpected troubles.
The phrase comes from the myth in which opening a sealed container releases harmful forces into the world. In everyday language, opening a Pandora’s box means beginning an action or investigation that creates many unforeseen complications.
The expression is metaphorical rather than a reference to a literal historical object. Its wording reflects the later tradition that changed Hesiod’s jar into a box. The phrase became especially useful in journalism, politics, law, and popular writing because it quickly signals a chain reaction of problems.
A common mix-up is “Pandora’s jar,” which is closer to Hesiod’s original account but is not the established English idiom. The modern phrase preserves the story’s warning about consequences that cannot easily be reversed.