You can meet people who are really beautiful. Then, when you see them angry for the first time, all of a sudden they're not beautiful anymore. They didn't just step into the other room and have plastic surgery; they're still the same physically. It's just that something inside of them has changed. They're no longer attractive.
All the different nations in the world, despite their differences of appearance and religion and language and way of life, still have one thing in common, and that is what's inside of all of us. If we X-rayed the insides of different human beings, we wouldn't be able to tell from those X-rays what the person's language or background or race is.