Long ago, magnetic fields used to be something for specialists and not necessarily for the ordinary astrophysicist. This has drastically changed over the past few decades. Nowadays, many people invoke the magnetorotational instability to explain turbulence and growth or at least the maintenance of magnetic fields in accretion disks or in core-collapse supernovae, for example. Star formation is another example where magnetic fields are crucial to making the gas collapse. Yet another example is stellar activity, where the presence of magnetic fields makes all the difference compared to just a radially symmetric solution to the stellar structure equations. Magnetic fields may even play a role in solving the Hubble tension, the difference between the measured values of 73 km/s/Mpc for the late Universe and 67.7 km/s/Mpc for the early Universe. In my talk, I will start with a historical perspective, going back to the days when the existence and origin of magnetic fields was still very obscure. We knew about the Earth's magnetic field since the 1600s, and astronomical observations have revealed magnetic fields in sunspots and eventually in other stars and galaxies during the last century. To understand their origin, people had to struggle with Cowling's anti-dynamo theorem that magnetic fields cannot be generated from kinetic energy in a simple axisymmetric geometry. Gradually, it became clear that in three-dimensional settings, self-excited dynamos do actually work. see the figure showing magnetic field vectors in orange and yellow, compared to vorticity vectors in white near a low-pressure tube in blue. Meanwhile, with the emergence of three-dimensional simulations, where the plasma motions tend to be turbulent, it becomes hard to think of any situation were magnetic fields would not exist! Dynamo action has now also been realized in the lab in various configurations. But some basic questions are still troubling us: why exactly is the Sun's magnetic field exhibiting equatorward migration and why do simulations not yet reproduce the large-scale magnetic fields observed in spiral galaxies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Brandenburg is available for meetings by arrangement with his host, Friedrich Roepke (roepke@uni-heidelberg.de)