During the first trillion-trillion-trillionth of a second, matter and antimatter flickered in and out of existence. The fate of the universe hung precariously in the balance, it might grow, or it might collapse back into nothingness. Suddenly it ballooned to enormous size (after all, we are here), in what cosmologists call the inflationary epoch, bringing the first true particles of matter — the quarks — into existence. Within a millionth of a second the rapid swelling ceased, and the quarks began to be confined to protons, neutrons and electrons. The universe continued to expand and cool, but now at a more stately pace. Already the universe was vastly larger than what we are able to observe today. Within a few more minutes, protons and neutrons combined into the first atomic nuclei — hydrogen and helium — but still the universe was too hot for the nuclei to shag electrons and make atoms. Not until 300,000 years after the beginning did the first atoms appear.
Irregularities in the gassy universe of hydrogen and helium were accentuated by gravity. Within a billion years after the beginning, the first stars and galaxies were born. There were not yet any Earthlike planets orbiting the stars of the earliest galaxies, because there were not yet significant quantities of the heavy elements (these would be cooked up later in stars). Nor had the Sun yet been born. But within a few billion years, the universe had begun to look familiar on the largest scale.
--An Intimate Look at the Night Sky, Boston Globe Science Columnist Chet Raymo
