The modern idiom “open Pandora’s box” means to begin an action that releases many new and difficult problems. It comes from the Greek myth in which Pandora opens a container holding destructive forces.
The expression is used in journalism, politics, law, science, and everyday conversation. It usually warns that investigating or changing one issue may produce consequences that are difficult to control or reverse.
The wording reflects the popular version of the myth rather than Hesiod’s original terminology. Hesiod described a pithos, a large jar, while later translations and retellings transformed it into a box. The idiom retained the box image because it is compact and easily understood.
“Open a can of worms” is a related English expression, but it is not the same phrase. It usually suggests creating a complicated mess, whereas “open Pandora’s box” carries the specific mythological association with releasing evils.