Once upon a time (4.6 billion years ago)...

Meteors began smashing into each other in the sky. Over time, this formed a HUGE chunk of rock that became the planet Earth. (It also formed its best friend, the moon, but that's a story for another day.)

The Earth then went through many amazing transformations, eventually ending with the evolution of us humans. But if we went through every single thing that happened, it would take all day. Let's just have a look at the major events in the history of that chunk of rock to see how the Earth we know and love today came to be.

Hadean + Archaean Period

Combined, these 2 periods lasted from 4.6 billion years ago to 2 . 5 billion years ago. During them, the Earth heated and cooled many times, and meteors brought strange crystals containing water and oxygen, which collected over time. But, try as it might, the Earth just couldn't manage to support life.

Chapter 1 - The Precambrian Era

Precambrian Era - Proterozoic Period

This period lasted 2 . 5 billion years ago to 542 million years ago. One day, a strange things began to happen to the meteors - they came with chemicals and proteins! These landed in the oceans and mixed together, eventually creating the very first life - bacteria! Over time, from these bacteria, more complex life evolved. Some even had simple skeletons! But, they couldn't go on land.

Paleozoic Era - Cambrian Period

This period lasted from 541 million years ago to 485.4 million years ago. During the Cambrian period, an amazing thing happened - the Cambrian explosion! This is the name for the time when life suddenly diversified into many different odd-looking animals.

The first fishes appeared, as well as the first animals with spines. Life was on its way to reaching land.

Chapter 2 - The Paleozoic Era

Paleozoic Era - Ordovician Period

The Ordovician period lasted from 485.4 million years ago to 448.3 million years ago. This time period was very important for every complicated life form. Many different families of animals were suddenly born. There was much more life in the oceans than there had ever been, but so far, nothing on the land. Would the Earth ever be able to get life out of the water?

Paleozoic Era - Silurian Period

The Silurian period lasted from 443.8 million years ago to 419.2 million years ago. During this period, for the first time, complex land plants were seen. Life had finally come to land! But there was still much more to be done to prepare the Earth for mankind.

Paleozoic Era - Devonian Period

This period lasted from 419.2 million years ago to 358.9 million years ago. During this period, another amazing thing happened. For the first time, an animal crawled onto the land! Called the Tiktaalik, this animal became the first amphibian and eventually evolved into the first animal to call the land its permanent home. Now there was both animals and plants on the land.

Paleozoic Era - Carboniferous Period

The Carboniferous Period lasted from 358.9 million years ago to 298.9 million years ago. During this period, plants suddenly diversified into the first trees and ferns! Also, land life was growing, and there were several reptiles that roamed the new forests. Insects existed as well, but they were enormous - a dragonfly could grow to the size of an eagle!

Paleozoic Era - Permian Period

For most of its time, which was 298.9 million years ago to 251.902 million years ago, the Permian period was good. Reptiles diversified into many different species, and it looked like some were going to evolve further into mammals. But then came something that shook our Earth to its core - the Permian extinction. It was a catastrophe of volcanoes and earthquakes that made 70% of land species and 90% of ocean species extinct. Could life ever recover from this crushing blow?

Mesozoic Era - Triassic Period

This period lasted from 259.1 million years ago to 201.3 million years ago. And, what's this? It looks like life has fully recovered after all! And, the first dinosaurs are here! Along with the dinosaurs evolved the first mammals, which would one day evolve into humans.

Chapter 3 - The Mesozoic Era

Mesozoic Era - Jurassic Period

The Jurassic period lasted from 201.3 million years ago to 145 million years ago. Dinosaurs were quickly claiming the Earth, and a new kind of animal appeared - birds! In fact, they say that the birds we see today evolved from dinosaurs. This was the height of the dinosaurs' domination of the Earth.