"Approximately 14.0 billion years ago, the universe came into existence. Prior to that, the Universe was nothing. The universe was formed in a massive expansion that resembled a balloon. Eventually the balloon burst in a massive explosion. In a fraction of a second, the universe grew at a tremendous rate, and is still growing today."
But what was the universe before the massive expansion?
"Great Question Julia. In fact, we don't know for sure, but one theory is that the big bang theory started with singularity. Singularity is infinitely hot and dense as well as infinitely small. One common misconception is that the big bang is a giant explosion. However, the big bang is just a large expansion of the universe that continues to this day.
Eventually our solar system was formed including the sun. Scientists believe the sun and solar System was formed by a giant rotating ball of gas known as the Solar Nebula. Eventually the Solar Nebula attracted particles and gravity pulled them into large masses now known as planets. Finally, plants and humans came into existence and earth we know today was formed.