Is there a way I can find out my grandfather's exact nationality?

Question:

Is there a way I can find out my grandfather's exact nationality?

We are not exactly sure what it is.

Best Answer - Chosen by Asker: Maria,

If your grandfather emigrated through Ellis Island, you can check the ship's manifests online. They often give the town, city, or village that the ancestor came from, as well as the nation. Don't go by the nation alone especially in Eastern Europe. My great-grandparents are reported to have come from the Austro-Hungarian Empire but they are neither Austrian or Hungarian, they're Slovak. Once you find out the town, city, or Village google it to find out what ethnic groups lived there. Other ways to find out: if you have access to his birth certificate, baptism, marriage military, or death records. These often give the birthplace. If you didn't know him, ask your parents if he ever spoke another language. That will be a big clue.