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.