We preview tonight's American Experience documentary on PBS titled "The American Diplomat," which highlights the significance of three African Americans who served as ambassadors or otherwise were part of our country's foreign service at a time when the presence of blacks was severely limited. Leola Carzolai-Stewart is director of the film. Dr. Michael Krenn, Professor of History at Appalachian State University, is author of the book "Black Diplomacy: African-Americans and the State Department, 1945-1969."