What modern expression, based on Pandora’s myth, means an action that creates many unexpected problems?

“Opening Pandora’s box” means taking an action that creates many unexpected problems.

The expression comes from the myth in which Pandora opens a sealed container and releases evils into the human world. In modern English, it is usually used metaphorically rather than as a reference to literal Greek religious belief. A government decision, scientific experiment, legal dispute, or personal choice may be described this way when it produces consequences that are difficult to control.

The phrase normally implies that the original action appeared manageable but had a much wider effect. It is related to, but not identical with, “opening a can of worms.” Both expressions describe complications, yet Pandora’s box carries a stronger sense of releasing numerous harmful consequences from a single source.

The wording preserves the later “box” tradition even though the ancient vessel was generally a large jar. The expression is now established in journalism, politics, fiction, and everyday conversation, making the myth one of the most widely reused stories from classical mythology.