Shahab Hosseini's family in San Francisco after immigration to U.S.

Immigration, in its simplest definition, is the movement of people from one place or country into another one. It is a simple yet fundamental aspect of human history. Immigration is a concept that pre-dates existing laws. Long ago, nomadic tribes traveled from place to place to find fresh and fertile lands, pastures for their livestock, and rich areas for hunting and fishing. In modern times, immigration still continues all over the world.