Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nf6/3. Nxe5/3...d6/4. Nxf7/4...Kxf7/5. d4/5...c5

5...c5
This move destroys White's center using the c-pawn. It also avoids Nxe4? Qh5+ when Black will lose a piece and still have an exposed King.