At this point, perhaps it is worth saying that there is no seamless transition between these "eras" of history. They are simply categorizations used by historians to differentiate between periods of time and general trends. No one at the time would have said, "Ah yes, we live in the splendid Classical Era." Or "there sure is a lot going on in the Middle Ages!" There are blurry lines demarcating these periods, and the developments often overlap. There is also both progress and regression between these periods. Civilizations grew once again, but there was no coherent political development. For example, China continued its trend of dynasties, while Europe fragmented into various kingdoms and states. There were also both continuities and changes in religion. Buddhism and Christianity continued to spread, and they were joined by Islam in the 7th century. The Silk Road (both overland and maritime) continued to be a conduit for culture, goods and ideas, and as before, no one empire or state controlled the trade. The introduction of the camel in Africa allowed it to develop its own version of the Silk Roads, the Trans-Saharan trade network. And the Americas had their own networks of exchange that connected cultures in North, Central and South America. In Oceania, a second wave of Polynesian migrations introduced new religious ideas and social structures to Hawaii. Thus, this period is characterized by expanding interconnections that would create both conflict and cooperation between regions and societies. 

Content Summaries part 1: The Byzantine Empire & Rise of Islamic Empires 

Content Summaries part 2: An Age of Religion & Recovery 

Content Summaries Part 3: AP World Period 1 part 1 (1000-1250)

Content Summaries Part 4: AP World Period 1 part 2 (1200-1450)