In the first moments after the Big Bang, the universe was extremely hot and dense. As it cooled, conditions gave rise to the building blocks of matter, quarks and electrons. A few millionths of a second later, quarks aggregated to produce protons and neutrons and in minutes these protons and neutrons combined into nuclei. As the universe continued to expand and cool, things slowed down and it took 380,000 years before atoms were formed when electrons were trapped in orbits around nuclei. These atoms were mainly helium and hydrogen, still the most common elements in existence. In the following half-billion years, clumps of gas collapsed enough to form the first stars and galaxies. In the hearts of these stars elements like iron, carbon and oxygen are produced which are then seeded throughout the universe following explosions called supernovae.
A little after 9 billion years after the Big Bang, our solar system was born.
We are currently finding out more about the invisible as well as the visible universe, through agencies like NASA (National Aeronautics and Space Administration) and CERN ( European Organisation for Nuclear Research) who investigate phenomena like dark matter which does not emit any electromagnetic radiation and dark energy, comprising a huge part of the universe that we can only detect through its effects.
Glittering crowded hub of our Milky Way galaxy - NASA