This book is a description of the objects that are part of a small museum being set up at the Department of Information, School of Engineering, University of Florence. It also includes several pages dedicated to the most notable computers of the past, though they are not part of the small museum. The title of the book suggests that there is a single sheet for each object. Unfortunately, this has not always been possible, so some pages contain more than one item, while some contain the opposite. In any case, each card has a number; for example, the card dedicated to the "AMD64 architecture" is number 38, therefore in the Contents it appears as ``38. AMD64 architecture''. To make cross-referencing easier, the card number of a given item is added (within parentheses) in the Index; for instance, near the "AMD64 architecture" is (38). A consistent part of the text is devoted to microprocessors, but also memories, storage media, systems or part of systems, and portable computers have a relevant space. Finally, the first pages are dedicated to the precursors, i.e., to the people who initiated the adventure of digital computers.