Citizenship and Immigration Services, United States, is a U.S. government agency that oversees immigration services, including the review and processing of citizenship applications and requests for work permits. The agency, sometimes called USCIS, regulates the entry of aliens (noncitizens) into the United States. USCIS was created by the Homeland Security Act of 2002, and it began operations in March 2003. It is part of the U.S. Department of Homeland Security.