Egypt was one of the empires that lasted for the longest. Despite many intermediate periods filled with uncertainty and problems, they always managed to put the empire back to pieces. Around 3100 b.c. - the history of a united Egypt began. The pharaoh Menes united Upper and Lower Egypt.
The first period "Early Dynastic Period' was hereby created. The cities were expanded, expeditions to the Levant was made, the workforce size was increased. The pharaohs power increased.
The next period 'Old Kingdom', is by several Egyptologists known as the greatest period in Egyptian History. This is the period where the Giza pyramids were built. If you want to read more about Egyptian history, click the link.