How did Persia change over time?

Answer 1

It expanded from being a tributory tribe to the Medes by absorbing Media, then using this combination to absorb the Babylonian empire, then Lydian Empire, moving on to encompass Central Asia and Egypt, finally stretching from today's Libya in the west to Pakistan in the east.

It was then taken over by Macedonia under Alexander the great. After his death his generals split up his empire into the Hellenistic Kingdoms which settled down to be Macedonia, Egypt, Syria (incorporating most of the Middle East) and some transitory ones in Asia Minor.

These kingdoms were progressively absorbed into the Roman Empire and the Parthian Empire.