“Open Pandora’s box” describes an action that creates many new and difficult problems.
The expression comes from the myth in which Pandora opens a container holding destructive forces or troubles. Once released, they spread into the human world. In modern English, the phrase is usually figurative: a person may “open Pandora’s box” by starting an investigation, debate, or process whose consequences become unexpectedly complicated.
The expression is related to, but not identical with, “Pandora’s box” as a noun phrase. The noun names the source of trouble, while the verb phrase describes the act that unleashes it. The wording is also based on the later box version of the myth, not Hesiod’s original pithos.
It is often used in journalism, politics, and everyday speech. The phrase does not usually suggest one isolated problem; it implies a chain or collection of consequences that may be hard to control.