The universe has gone through several major eras over its history. These eras are: the planck era - the time before second when we require a theory of everything to describe what happened. The era ended when the strong force froze out of gut force, leaving three forces operating (gravity, strong, and the electroweak force). At the end of the particle era, all of the quarks in the universe combined into protons and neutrons. Eras (ii: the era of nucleosynthesis during this era, the temperature of the universe remained so high that nuclei broke apart as quickly as they formed. This era ended when the universe became too cool for fusion to occur. Photons bounced rapidly from one electron to the next, never getting far. The atoms formed into galaxies due to slight density enhancements: the era of galaxies this is our current era. Stars build nuclei into heavier elements and planets form around the stars.