Abstract: In the first part, I am going to explain basic facts on Littlewood-Paley theory. In the second part, I am going to explain Fujita-Kato Theory. Finally I am going to explain Cannone-Meyer-Planchon theorem of Navier-Stokes systems. I am going to explain my most recent result on 3-D anisotropic Navier-Stokes system if time is allowed. I am going to give 3 two-hours' lecture by black board.