When they flood, they make the surrounding soil fertile. They're suitable for agriculture. And the Nile Valley is one of the first places that we see agriculture emerging during the Neolithic period. In fact, human settlement, we believe, was along this Nile River Valley as far as 6,000 BCE, or 8,000 years ago. And it might have been there even further back in time. And because you had that agriculture, it allowed for higher population densities, which allowed for more specialization of labor and more complex societies. It's not a coincidence that some of the first, that one of the first great civilizations emerged here.