Planets are common astronomical objects. Gas giant planets, which are massive planets made of mostly hydrogen and helium, are the first planets to form, and due to their large masses, they affect the dynamical evolution of young planetary systems. In addition, giant planet composition reveals key information on the birth environment of planets. In this talk, we will briefly explore giant planet formation, evolution and interior models. We will see that giant planets are complex objects that can have composition gradients and fuzzy cores, and that their internal structure and evolution depend on their growth history. We will also find out about new structure models of Jupiter that fit the planet’s gravity data as measured by the NASA Juno mission, and learn how they reveal information on Jupiter’s origin and evolution.