COVID-19 is not, by far, the deadliest pandemic in history, but it is the worst we have experienced. It is our black plague. An enemy that we did not see coming and that generates many doubts about its forms of attack and its weak points. But the coronaviruses that now concern us are not new: years ago they already staged two alarming outbreaks when they "jumped" from an animal to a human being. Now, a new mutation (SARS-CoV-2) has spread much faster than its predecessors and seems poised to destabilize all of our lives. The authors offer us an informative journey through this microscopic reality that now threatens us. How a virus acts and spreads, the diagnostic tests that exist, research on vaccines, what foods protect us, past pandemics —or possible future ones— are some of the aspects that await us in this book.