The story of the universe is a tale of fundamental particles and forces, from the first moments of the big bang to the formation of the first atoms. It is a story of how the universe cooled and expanded, allowing for the formation of protons, neutrons, and electrons, and how these particles combined to form the first atoms. It is a story of how the universe's structure was seeded by tiny temperature variations in the early universe, and how these variations grew into the vast superclusters of galaxies we see today. It is a story of how the universe's history is written in the cosmic microwave background, the faint afterglow of the big bang, and how this radiation provides a window into the universe's past.