What has been humanity's greatest enemy throughout time? Believe it or not, these terrible historical figures have neither a human voice nor a human face... They are the most fearsome viruses, bacteria, fungi and protists whose greatest purpose is the extermination of humanity! In this book you will learn more details about the battles that we have managed to win against several of these enemies, and a couple of cases in which we have not gone as well as we would have liked. Written in a fun tone and complemented with colorful illustrations, this is an introductory work to the history of our complicated relationship with these microscopic beings, both the bad ones and those who have joined our ranks to combat the different diseases caused by the enemy.