What expression means to start a process that creates many unforeseen problems, like Pandora’s box?

“Open Pandora’s box” means to start a process that creates many unforeseen problems.

The expression comes from the Greek myth in which Pandora opens a container and releases destructive forces into the human world. In modern English, it is usually used figuratively rather than to describe the myth itself. A government decision, scientific experiment, or personal action may be called “opening Pandora’s box” when it creates consequences that are difficult to control.

The phrase is related to, but not identical with, “let the genie out of the bottle.” Both expressions describe an irreversible release, yet they come from different stories and carry different imagery. “Open Pandora’s box” specifically suggests a cascade of troubles or complications.

The familiar word “box” is a translation-driven development. Hesiod described a pithos, or large jar, while the Renaissance scholar Erasmus helped establish the Latin and later European box tradition.