Each year, tens of thousands of unaccompanied children arrive at the U.S.-Mexico border, often making a long and perilous journey from Central America. Amna Nawaz interviewed a group of sisters who undertook this trek alone, with three young girls aged 8 to 14 traveling 1,500 miles from Southern Mexico to the U.S. border to reunite with their mother who had moved to the United States years earlier.