We study global existence of smooth solutions to the 3D Vlasov-Poisson system. We introduce "the good, the bad and the ugly" decomposition following the proof given in Glassey`s book, a modification of Schaeffer`s simplification (1991) of Pfaffelmoser`s original proof (1992). Reference: Robert T. Glassey, The Cauchy Problem in Kinetic Theory https://snu-ac-kr.zoom.us/j/4020312420