What common English expression means releasing many unforeseen problems, as in the Pandora myth?

The English expression is “opening Pandora’s box,” meaning to create or release many unforeseen problems.

The idiom comes from the myth in which Pandora opens a sealed container and harmful forces spread through the world. In modern usage, someone “opens Pandora’s box” by taking an action that begins a chain of difficult, unexpected, or uncontrollable consequences.

The expression is figurative rather than a claim that the myth describes a literal historical event. It appears in discussions of politics, technology, law, science, and everyday decisions when one change produces many complications.

The wording also preserves a translation change. Hesiod described a pithos, or large jar, while later Latin translation helped turn the vessel into a box in European retellings. “Opening Pandora’s box” is therefore a modern English phrase built from both the ancient narrative and its later transmission.