The term Late Antiquity is the transitional centuries from Classical Antiquity to the Middle Ages in both mainland Europe and the Mediterranean world: generally from the end of the Roman Empire's Crisis of the 3rd century (c. 284) to the Islamic conquests and the re-organization of the Byzantine Empire under Heraclius that occurred in the seventh century. The beginning of the post-classical age (known as the Middle Ages for Europe) following the fall of the Western Roman Empire spanning roughly from 500 to 1500. Aspects of continuity with the earlier classical period are discussed in greater detail under the heading "Late Antiquity".