Juno was launched in 2011 and arrived at Jupiter in 2016. Since then it has been studying the planets interior, it's cloud patterns, weather, radiation environment and so much more.
Juno has already completely revolutionized our understanding of this gas giant as well as given us some absolutely breathtaking images. Before Juno we had not been able to get a good image of either of the planet's poles. This is what we have now.
Since it's arrival, Juno has helped scientists discover that:
Jupiter's weather goes much deeper than expected.
It's gravity and magnetic field are somewhat lopsided.
It's auroras are much more energetic than expected.
Its atmosphere contains far more oxygen than expected.
There may be metallic hydrogen at it's core.
And so much more about the planet and it's massive system of moons.
The mission is planned to run until 2021 but may gain another extension.