There are many theories as to what could be inside a black hole. Although there is no official evidence, some theories seem plausible and could change everything we know about our universe. One major theory is that inside every black hole is a universe. Meaning that our entire universe is within a supermassive black hole, which is then within a parent universe. Some of the unsolved questions that correspond with the big bang have been answered with the black hole theory. There are two central theories that the big bang does not solve.
First, general relativity has to do with gravity. It describes the universe at the largest scales. The sun for instance causes distortions in spacetime which alters the motion of Earth. It is the sun's pull that creates what we know as the force gravity. Secondly quantum mechanics describes the universe at the smallest scales. Since these are two separate theories, physicists have been trying to figure out a way to combine the two to make "quantum gravity". In order for physicistis to get a hold on "quantum gravity" and whether it could exist, they had to look at torsion. Torsion is what causes spacetime to twist.
In the beginning, the tension between the spinning and turning of spacetime caused repulsive forces. The attraction from curved space would at first subdue the repulsion from torsion, causing matter to collapse into smaller regions. Eventually torsion would become stronger and since energy can be converted into mass, the high gravitational energy would create an increasing mass inside the balck hole. As torsion builds up the compression would stop and have a bounce back effect creating the ever expanding universe that we see today.
In theory, the idea that every black hole contains another universe seems a little extreme, but it also answers several unknow questions. Could our universe be within another?