What happens at the center of a black hole?

Center of Milky Way found to be brimming with black holes

Anatomy

What happens at the center of a black hole?

There must be a singularity at each black hole's center - Big Think

Dozen black holes found at galactic centre

NASA Supports Event Horizon Telescope in Studying Milky Way's Black Hole

What is a black hole? University of Chicago News

What's in the Center of a Black Hole?

What exactly is inside of a black hole? What is it made up of? - Quora