In the idiom “Pandora’s box,” opening the box metaphorically releases troubles.
The expression comes from the Greek myth of Pandora, in which opening a container allows harmful forces to escape into the world. In modern English, “opening Pandora’s box” means starting an action or investigation that produces many unexpected problems.
The phrase is often used even when no literal container is involved. A political decision, a scientific experiment, or a legal dispute may be called a Pandora’s box if it creates consequences that are difficult to control or reverse.
The familiar English wording is also based on a translation history. Hesiod’s Greek account refers to a large storage container, traditionally identified as a pithos, rather than a small hinged box. Renaissance and later European translations helped establish the expression “Pandora’s box,” which became the standard form in English.