We covered one of the most important milestones in the history of cosmology, the discovery of the microwave background by Penzias and Wilson (they later won the Nobel Prize for this achievement). This confirmed the theory of the Big Bang as the birth of our Universe. We then discussed the first few seconds after the Big Bang and the production of matter and antimatter in slightly unequal amounts which resulted in the formation of the first stars and then galaxies. We then covered the fact that until 380,000 years after the Big Bang radiation and matter were coupled, and hence we cannot directly observe anything before that time, so we have to build on our current knowledge of physics to infer the physical processes that occurred.