Because Egyptian history lasted so long, Egyptologists divide the historical timeline into three periods called kingdoms: (1) The Old Kingdom, (2) The Middle Kingdom, and (3) The New Kingdom.
The Old Kingdom saw the beginnings of nationhood for Egypt under one supreme ruler, the Pharaoh. This period saw the rise of the Great Pyramids and established rules for Egyptian art that would last for 3,000 years. The Middle Kingdom was a period of stabilizing after the Old Kingdom collapsed, and saw a nation fighting to regain its greatness. Pyramids were still built, but not to the same quality as those built during the Old Kingdom. Being built of mud-brick instead of stone, they would not last as long. During this time, the power of the priests of Amun began to overshadow the kings, and the country was eventually split again.
Through the rise of the New Kingdom, Egypt developed a golden age of prosperity. The greatest pharaohs the country would see ruled during a time of incredible building projects and beautiful artistic craftsmanship. The pharaohs of the New Kingdom ceased building pyramids and focused on tombs in the famous Valley of the Kings. Through the power of their great army, the pharaohs exerted their authority over lands in the Levant and south into Nubia.
Separating each of these kingdoms were Intermediate Periods that sent their country into chaos. These 'dark ages' plague scholars due to the lack of written records available, but what we do have indicates that the people experienced economic hardships until stability could be restored. After the New Kingdom, Egypt experienced its Third Intermediate Period where it saw a rule by Nubians, Assyrians, and Persians before finally becoming a province of the Roman Empire.