This is an introduction to the series of 15 papers that follow. These report scientific results from the fields-and-particles instruments on Cassini/Huygens. For these works, their data acquisition started as early as 16 months before the passage by Jupiter and, for some, continued up to the approach to Saturn. The flyby of Jupiter provided a gravitational assist, which was necessary for the spacecraft to reach its destination, the Saturnian system. In addition to the scientific results, the Cassini/Huygens team gained much because Jupiter provided a dress rehearsal for skills needed at Saturn. The flyby also fostered international cooperation between the Cassini/Huygens teams, the Galileo teams, and the scientific teams using instruments in orbit about the Earth and on the ground. A number of important discoveries and insights came from these cooperative efforts. The boundary physics and compression of the Jovian magnetosphere was observed by both fields and particle instruments. The propagation of the solar wind between Earth and Jupiter was studied. The source of Jovian radio emission was further characterized. The first images of energetic neutral atoms at Jupiter were obtained.