This question is surprisingly complicated!  You may have heard something about the black hole’s center, often called the singularity.

Mathematically, the density goes to infinity at the singularity.  But here we run into a problem: infinite density doesn’t make any physical sense!  So, we believe that the singularity doesn’t actually exist and the density is not infinite at the center.  So what happens instead?

Unfortunately, the conditions are so extreme at the black hole’s center that our theories break down.  It doesn’t help that the black hole’s center is located within the event horizon, which is the region that light can’t escape from.  So, we will never be able to actually see it.

Long story short, at the black hole’s center, physics gets so weird that we don’t exactly know what happens!