They are average men and women, stable, educated, born in the United States and they are jihadists. This is the face of homegrown terrorism. Peter Bergen is CNN's national security analyst and one of the most respected authorities on terrorism. He reveals the surprisingly banal beginnings of these radicalized citizens and the disturbingly difficult job authorities have in tracking them down. His new book is called The United States of Jihad: Investigating America's Homegrown Terrorists.