A mini black hole roughly the mass of a thousand sedans at a size that is smaller than an atom. At that size the black hole wouldn't swallow much matter and would instead mostly trap atoms and some larger molecules into circling orbits in much the same way that protons in atoms capture and bind electrons. These mini black holes show up all around Earth every day, but they’re so little that no one can see them and they aren’t causing damage, so they aren’t worrisome.