Around 13.8 billion years ago a singularity the size of an atom existed. This singularity know as the Big Bang caused an explosion so great that it caused the expansion of space and created the universe we observe today.
Before the stars, galaxies and all the matter in the universe there was a period known as the dark ages. During this period of time no light shone in the universe.
As the universe began to cool, the gas clouds began to condense and the Hydrogen and Helium atoms began to fuse in nuclear fusion giving birth to the first stars in the early universe.
Around 200-500 million years after the Big Bang and as the first primordial stars went supernova, the first galaxies began to form.
13.8 billion years after the Big Bang, humans now inhabit the planet we call Earth inside of our own galaxy known as the Milky Way, containing an estimated 100-400 billion stars and an estimated 100 billion planets