The book that you hold in your hands tells about a strikingly interesting life, a life closer than anyone else, but at the same time, oddly enough, most of us are unfamiliar, a life that is very dependent on our behavior and at the same time sometimes completely independent of us. The famous popularizer of science Rafail Nudelman wrote a book about our one-of-a-kind property - our body. Why does it yawn, hiccup, sneeze, why does it hurt? Exactly why and for what - and not why... And also - why does our body need bacteria, for which almost the entire periodic table is needed and what benefit can the hemoglobin gene spoiled by the mutation bring to it?..