Stephen Hawking has theorized that throughout a black hole's lifetime, it will emit a sort of "black body radiation." This is known as Hawking radiation, and will be responsible for the ultimate decay of the black hole. Depending on the size of the black hole, at the end of its life, it will vaporize in a white flash of light. The largest supermassive black holes will vaporize well after a googol years.
Some physicists have suggested that as a black hole vaporizes, the energy that was previously stored within the singularity is released through a "white hole." Black holes and white holes are reciprocal. You can think of the Big Bang as a white hole.