Each star has different physical characteristics, which are determined by its initial mass. From tiny red dwarfs to certain supergiants that could “squeeze” hundreds of millions of stars like the Sun inside them, the variety of stars out there is truly vast. In this episode of the Space Series, we will see that, unlike the Sun, most stars do not wander alone through interstellar space, but are born in systems of two, three, and, more rarely, more stars, which orbit around their common center of mass. We will also see that binary systems, in particular, can trigger some of the most powerful stellar explosions known to us. Finally, we will see that groups consisting of many more stars often form, which astronomers call star clusters.