Can You Make a Black Hole Out of Anything?

We think that you can make a black hole out of basically anything, if you make it dense enough. There might be a minimum size to a black hole - but we've never seen one at all. They could have been ad in the very early universe,. these primordial black holes that could be very, very small up to very, very large sizes. We don't see very many black holes out there that are like the mass of the earth. That doesn't mean they're not out there.