The book is intended to be used by both students and experts in the covered fields. It consists of an updated view, as far as anticancer or antibacterial activities are concerned, of onions. It also approaches the bacterial toxins as important actors of syndromes and disease in humans, as well as the description in an updated fashion, of a new form of fighting the microbial infections, such as pyroptosis. The book goes then into the several ways that we have to render the microbial pathogens susceptible to antimicrobials, as well as new possibilities to overcome the development of resistances to new antibiotics. The main objective of this book is to provide both a background and an update on some critical areas of microbiology currently affecting our health and welfare. The book contains enough classical and new materials in different fields of Microbiology (including viruses), food-caused allergies, resistance to antimicrobials, and how to cope with them.