How did nationalism and anti-imperialism emerge and manifest themselves?

Nationalism and anti-imperialism started manifesting in the 19th century around the idea that people of different ethnicities share a same culture and the same history and should be independent from others who were not their people. This was seen in Europe in places such as the Austria-Hungary and the Ottoman empires where they controlled numerous people from various ethnic and cultural backgrounds. These groups started developing their pride for who they are and started fighting for independence.