Parasites and symbionts belong to the realm of fantasy. When we see these creatures up close, they make us afraid and disgusted. When we learn that worms or invertebrates can live in us, we panic. In reality, everything is regulated and governed by the will of the human body. Parasites, of course, act like occupiers of our organism—but the body’s defense system is also complex and ingenious. This book is a guide to the main “enemies”: it describes their strengths and weaknesses, tells stories about how invasion may happen, and the ways to defend against it. Dive into the fascinating wild-wild world of our organism—accept it or fight it!