Professor Brian Cox journeys to Southeast Asia to see how life began on Earth and how the flow of energy created and supports life.

Brian travels to Africa and Madagascar to analyse why Earth is a fertile place and how it allows complex life to exist.

The fourth episode sees Brian in Australia looking at how the size of life affects each plant and animal, and how long it can survive.

In the final episode, Cox explains what makes Earth a home for life and asks what ingredients were required for complex life to begin.