In the phrase “open Pandora’s box,” what does the box metaphorically release?

In the phrase “open Pandora’s box,” the box metaphorically releases unforeseen troubles.

The expression comes from the Greek myth in which Pandora opens a container and lets diseases, suffering, and other hardships spread through the world. In modern English, the phrase describes an action that appears limited or harmless but produces many complicated and damaging consequences.

The expression is usually applied to decisions, discoveries, arguments, or policies that create problems difficult to control once they begin. It does not normally mean that one single bad event occurs; it suggests a cascade of consequences.

The wording also preserves a translation history. Hesiod’s Greek story used the word pithos, meaning a large jar or storage vessel. Renaissance translators helped popularize “box,” and that version became the standard form in English and many other languages.