This video commemorating the arrival of Juno at Jupiter is mostly stitched together images from JunoCam during the approach, up to the point where the instruments were switched off to protect them during closest approach, clearly shows the motion of the four Galilean Satellites: Io, Europa, Ganymede, and Callisto. It alludes to why they are important — they were visible to Galileo through his little refractor, and he could clearly plot their motion around Jupiter rather than Earth. It was the first really irrefutable evidence of objects orbiting something other than the Earth, and monumentally important. Galileo spent the rest of his life looking for more objects orbiting celestial bodies; his ultimate goal was to find planets orbiting stars. He never did — he could not possibly have appreciated the true size of the Universe. But he was the first to record observations of these moons of Jupiter.
And today, years after his namesake spacecraft made its final plunge into Jupiter, we can study the Jupiter system all over again, seeing it with new eyes and new instrumentation. There’s no telling what we may find!