It is said that a great value lies in little things. It's the case of screws, nuts, bolts: small objects that nowadays seem to hold together the whole world. The author, who has devoted a lifetime to this kind of hardware, tells us the story of the screw, from its ancient or even mythological origins, in pages full of facts and curiosities. His personal experience and memories are also linked to the history of the city of Florence and in particular of the famous Galileo industries.