Gaseous giant planets are a large planetary family. Formed in gas-rich protoplanetary disks, they bear lots of similarities to late-type, convective dwarf stars. However, because of their complicated molecular compositions, unique thermal conditions and fast spinning, gaseous planets have remarkably rich external and internal features, which are connected to a series of fundamental planetary physics puzzles such as zonal circulation, hydrogen-helium phase separation, inner-core erosion and dynamo processes etc. In our Solar system, there are two typical gaseous giant planets, namely, Jupiter and Saturn, which have already been closely explored by spacecrafts. Juno and Cassini missions are the two recent explorations to Jupiter and Saturn respectively. Their observations of the planetary outer spaces, moons, atmospheres, gravitational fields, magnetic fields, and deep interiors have been unprecedentedly precise and detailed. With the latest observational data, our knowledge of gaseous giant planets has been dramatically updated. But meanwhile, several fundamental puzzles remain highly disputed. The fast-broadening horizon of the subject is calling for smart scientific ideas and advanced future-exploration technologies. In this talk, the latest developments of relevant researches are reviewed. Emphasis is to be especially put on intricate and subtle distinctions between different individual planet.