A very short early history
The first seconds and minutes
These assumptions make it possible to calculate the history of the cosmos after a certain epoch called the Planck time. Scientists have yet to determine what prevailed before Planck time. Britannica
For a fraction of a second, the universe expanded faster than the speed of light. We do not know what triggered that initial, rapid expansion, but this period, called cosmic inflation, explains much of what we see in the universe today. NASA The detailed properties of CMB maps are consistent with the predictions of inflation. However, the physical process behind inflation remains unknown. NASA WMAP results support inflation: the idea that the universe underwent a dramatic period of expansion, growing by more than a trillion trillion fold in less than a trillionth of a trillionth of a second. NASA
What started inflation?
A NASA Hubble page says that for a fraction of a second the universe expanded faster than the speed of light, and that we do not know what triggered that initial, rapid expansion, called cosmic inflation. A NASA Physics of the Cosmos page says CMB maps are consistent with inflation’s predictions, but the physical process behind inflation remains unknown. WMAP results, NASA says, support the idea of a dramatic early expansion. Support for the idea is not the same as knowing what caused it.
About one second after the big bang, the rapid expansion slowed. The universe was an extremely hot, uniform, cosmic soup of subatomic particles and light. NASA
A few minutes after the big bang, the universe had cooled enough for subatomic particles to form atomic nuclei. Protons and neutrons formed the nuclei of hydrogen and helium, the basic building blocks of stars. NASA After a few seconds, the universe cooled enough to allow the formation of certain nuclei. The theory predicts that definite amounts of hydrogen, helium, and lithium were produced. Their abundances agree with what is observed today. Britannica
A few seconds, or a few minutes?
A NASA Hubble page says that a few minutes after the big bang the universe had cooled enough for subatomic particles to form atomic nuclei of hydrogen and helium. Britannica’s big-bang model article says that after a few seconds the universe cooled enough to allow the formation of certain nuclei, and that the predicted amounts of hydrogen, helium and lithium agree with what is observed today. “Seconds” and “minutes” are both in the sources. We report both.
Helium nuclei were created in the Big Bang and contain two protons and two neutrons each. Helium is the second most abundant element, comprising roughly one quarter of the mass of the universe. NASA
The chemical elements of life were first produced in the first generation of stars after the Big Bang. Those first stars produced the other chemical elements besides hydrogen and helium. NASA