The so-called Age of Discovery eventually brought four continents into contact: the Americas, Africa and Europe. There was some early colonization, but much of this period involved exploration and encounters between the people of these different continents. The documents are mostly divided into the causes and course of "discovery" and then the new encounters between Indigenous Americans, Europeans, and Africans. Significantly, this period marks the beginning of the Columbian Exchange, as people, plants, animals, ideas, and pathogens traversed the Atlantic.