The fifth and final era in the evolution of the Universe. This era will begin sometime around 10^100 years ABB (After the Big Bang), as the last of the supermassive black holes evaporates by Hawking radiation. The few remaining quarks will be the first to decay into energy, followed by the last of the leptons. Almost all the free energy of the Universe will be in the form of photons. Gamma rays will break down into X-rays, which will decay into visible light, and so on. Finally, the photons will be of such low energy that they spread across the entire Universe evenly. As the Universe continues to expand, the energy of the Universe will spread thinner and thinner, and the temperature will creep ever-closer to absolute zero. The Heat Death of the Universe will have arrived.
The preceding era will be the Black Hole Era, and there will be no succeding era.