COVID-19 has made us all aware of the fact that we live in a world full of invisible enemies. Normally, we don't even realize they're there, but from time to time one of these microscopic creatures becomes powerful enough to turn everything upside down. What are these invisible enemies, and how can we prepare ourselves for the pandemics of the future? A specialist in the cellular biology of diseases, Salvador Macip explains, in a language everyone can understand, what it means to share the planet with millions of microbes - some wonderful allies, others terrible foes. He provides a concise account of epidemics that changed history, and focuses on the great modern plagues that are still causing millions of deaths every year, from influenza, TB and malaria to COVID-19. Macip also examines the methods we have used - from vaccines to improved sanitation and social distancing - to try to control these invisible enemies. This authoritative overview of modern epidemics and the pathogens that cause them will be essential reading for anyone who wants to understand our world today, a world in which some of the greatest threats to the human species come from the invisible microbes with which we share this planet.