Historical Diffusion

What exactly is historical diffusion? There is no short answer to this question. Historical diffusion itself takes a very long time on its own. It all starts when there is an innovative idea that reaches a different country from which originated. Soon a small population of the whole country for example uses that idea to improve there lifestyle. Only a few people used the idea because it was from a different country. But the idea was so good that it caught on with more and more people. Soon the culture that is using the new idea has some influence from the other culture from which the idea came from.