This is an overview of how the natural world works, seen in the context of how we - humans - fit into it. It begins with the micro issues, a close-up of DNA, genes, viruses and cells, and then moves out to explore the larger systems of human biology: sex and reproduction, the brain and behaviour, and energy. Finally, we stand back and take a look at the species Homo sapiens from the revealing viewpoints of ecology, evolution and sociobiology. The result is an accessible portrayal of ourselves that enables readers with an interest, rather than a background, in science to become bioliterate and able to understand the discoveries that are making headlines in the news today.