The universe, now about 91 billion light years in diameter, began as a hot and infinitely dense point. When this tiny singularity violently exploded, all matter, energy, space and time were created. Following this explosion came the radiation and matter eras.
The radiation era is made of smaller stages which include the inflationary stage which all occurred in the early stages of the formation of the universe. The earliest stage of the radiation era is known as the plank epoch where only energy and the superforce existed. At the end of this stage, gravity split from the superforce and soon the strong nuclear force also split, and this commenced the inflationary stage. The inflationary stage started around 10^-36 seconds from the start of the big bang and the temperature was around 10^33Kelvins and during this stage, the universe expanded rapidly and cooled down at the same time. During this time, matter and energy cooled down enough to be able to separate from each other and the formation of matter and antimatter took place. Initially, the split between matter and antimatter was around half but as there was slightly more matter, upon collision between matter and antimatter they would annihilate each other and create energy, and therefore we only see the matter that did get annihilated. As the universe continues to cool and expand nucleosynthesis occurs and hydrogen forms but as it’s still too hot for electrons to orbit the proton as it’s still too energized, deuterium forms instead with one proton and one neutron. During this process helium is also formed. Around 100 seconds after the start of the big bang, the temperature had cooled down to about 10^9K and there were now electrons and positrons which were annihilating each other and creating photons but according to scientists it was impossible to see anything even with the production of photons and so that time period was known as the cosmic dark ages which went on for quite a while.
Around 50,000 years after the Big Bang, the temperature had cooled down to about 3000K for electrons to attach to the nuclei and so all these positively charged ions could now grab an electron and become neutral. This meant that any radiation that was already trapped there could escape as it was no longer charged. The formation of hydrogen and helium had created atomic clouds and due to the gravitational forces, the atoms would form clusters and then turn into galaxies. Over the next hundreds of millions of years, the formations of stars begin to take place due to the attraction between particles and the universe continuing to cool and expand. The Big Bang created hydrogen and helium however, to form heavier elements stars were needed. As stars evolve they take hydrogen and make helium with it. The bigger stars can take helium and turn it into bigger elements such as carbon and oxygen and the most massive stars can take those elements and combine them to make elements as heavy as silicon and iron. Once these heavier elements are built and collected over billions of years and lifetimes of stars, there are enough elements to form solar systems.
One thing that was not addressed was what came before the Big Bang, and that is because there is no definite answer yet. However, there’s one study from Oxford that found circles in CMBR and they believe these circles could be from the previous universe. Supermassive black holes from the end of the previous universe could possibly be the reason for these circles and they believe that the process of the universe collapsing and a new one forming is a continuous process.
https://phys.org/news/2010-11-scientists-glimpse-universe-big.html
The link I attached below is an interesting read on what could be on the other side of the Big Bang also published by Oxford University:
http://www.ox.ac.uk/news/science-blog/other-side-big-bang
References:
Hasan's thoughts and analysis of science related topics 