The expression “to open Pandora's box” usually describes starting what?

The expression “to open Pandora's box” usually describes starting a cascade of unforeseen problems.

The idiom comes from the Greek myth in which Pandora opens a vessel and releases evils into the world. In modern English, it is used figuratively for an action that creates many complications, dangers, or unintended consequences. The expression does not normally refer to a literal container.

The wording also preserves a historical transformation. Hesiod's original story involves a pithos, or large jar, but later Latin and European retellings popularized the idea of a box. As the image changed, the phrase became easier to use in everyday speech and writing.

The idiom is not a claim that every new discovery is harmful. It specifically suggests that opening or beginning something unleashes problems that are difficult to control or reverse. That figurative meaning is why the phrase appears in journalism, politics, science, and ordinary conversation.