NASA E/PO, Sonoma State University, Aurore Simonnet
One contender for the smallest thing in the universe is the singularity at the center of a black hole. (Shown here, an artist's drawing of a black hole pulling gas away from a companion star.)
They're thought to be what anchors galaxies - some of the largest objects in the universe.
And what happens past their event horizon, also known as the point of no return, can only be speculation since we will never get a chance to see it with our own eyes and live to tell the tale.
Despite decades of research, these dynamic cosmological phenomena are still shrouded in mystery. They're still blowing the minds of scientists who study them and here are ten reasons why.
Randy Astaiza contributed to an earlier version of this post.