Egypt is mostly desert, but a thin green strip runs through it from south to north. That strip is the Nile and the land it waters. Almost every Egyptian lives along the river or in the wide delta where it meets the sea. Photos taken from space show Egypt looking like a green flower on a sandy stem.
The Nile is unusual because it flows the 'wrong' way - north. Most big rivers in the world flow south. The Nile starts deep in the African highlands and flows all the way up through Sudan and Egypt before pouring out into the Mediterranean Sea.
For thousands of years, the Nile would flood every summer, spreading a layer of dark, rich mud across the fields. When the water went down, the fields were ready to grow wheat, barley, onions, melons and lettuces. Egyptians called the mud 'the gift of the river'.
The Nile is full of life. Crocodiles, hippos, kingfishers and pelicans live along its banks. Wooden sailing boats called feluccas still glide across it. Cities, farms, ancient temples and tiny villages all line its edge, the same way they did 4,000 years ago.