United States. Federal Bureau of Investigation

Created in 1908 within the Department of Justice, the Federal Bureau of Investigation grew from a small team of investigators into the United States' principal federal law enforcement and domestic intelligence agency. Its mission today includes protecting the country from national security threats, enforcing federal criminal laws, and supporting law enforcement partners across the nation.

The FBI became especially prominent in the 20th century as it pursued interstate crime, public corruption, espionage, organized crime, and later terrorism and cybercrime. The long tenure of director J. Edgar Hoover helped define the bureau's image as a modern investigative force, but it also left a complicated legacy because of surveillance abuses and political overreach that later drew intense criticism and reform.

That mix of public fascination and controversy is part of what makes the FBI such a compelling subject. Its history includes headline-making investigations, scientific and forensic advances, and constant tension between security, civil liberties, and public trust.