Parshat Va'eira tells about Aaron performing miracles in front of Pharaoh, and how he turns a stick into a snake.
So what's Pharaoh's response? "Big deal!" he says. "Egypt is full of magicians!" At which point Pharaoh calls in his young children who proceeds to also turn sticks into snakes!
Now, God certainly knew of Egypt's advanced knowledge of magic. So why did God have Aaron perform feats that could be so easily replicated?
The answer is that God wanted the Egyptians hooked into thinking that they could match Moses and Aaron step-for-step, so that later - when Moses and Aaron would perform greater miracles - the expert Egyptians would fully appreciate God's enormous powers.
And that's exactly what happens. After the third plague of lice, Pharaoh calls in his magicians to duplicate what Moses and Aaron had done. But they are unable to do so. At which point the magicians turn to Pharaoh, acknowledge God's awesome, infinite, power, and declare, "It is the finger of God."
The Talmud explains that the lice were too small for Pharaoh's magicians to manipulate. In a way, that's similar to our world today. Science produces so many magnificent wonders - atomic energy, space flight, genetic engineering. Yet it's all predicated on using existing energy and resources. So where did all that original matter come from?!
That's where God comes in. To create something out of nothing - the miniscule building-blocks of life - that is something of which only God is, was and will ever be capable. The encounter between Aaron and Pharaoh teaches us not to lose that perspective.