We still have a lot to understand about how the Solar System came to be, how planets and their moons generally form in the Universe. We know planets form in gas-dust disks around nascent stars (that we call circumstellar disks), and similarly, moon-systems of the giant planets assemble in disks around the forming gas giant planets (in so-called circumplanetary disks). The circumplanetary disks have multiple importance. First, they channel material to the forming planet, hence it influences its formation timescale and how big the planet can grow. Second, it is the birth nest for moons to grow, hence it influences the moon-formation timescale as well as the characteristics of these satellites. Third, the circumplanetary disks are surrounding the young, forming planets, hence they influence the observability of nascent planets. In my group, we are using 3D hydrodynamic simulations with radiation transport to better understand planet- and moon-formation, and how these forming systems can be detected.