CIA is the Central Intelligence Agency of the United States, and FBI is the Federal Bureau of Investigation of the United States. The targets of the CIA are mainly foreign countries, which in common terms are spies, involving politics, military, technology and culture. Including planning coups in other countries (such as Eastern Europe), stealing other countries' military secrets, etc. The FBI targets the United States. Since the United States is a federal system and each continent has its own legal and judicial independence, there is a hole for transcontinental crimes. The United States established the FBI specifically to prevent transcontinental crimes. Due to the development and changes in the domestic situation in the United States, the Joint Investigation Bureau has expanded from its original single police function to assume the important task of U.S. homeland security. For example, domestic counter-terrorism, smuggling, drugs, and even economic crimes, political crimes, etc. are included in the scope of the FBI's work. The FBI has trained a large number of agents (different from spies) in order to more effectively prevent various crimes. These agents are undercover agents in the terminology of Hong Kong police and gangster movies. However, American agents are not the exclusive domain of the FBI. The CIA also has agents. Most of the agents who appear in Hollywood blockbusters belong to the CIA, and most of their activities are abroad.