Book excerpt: This book focuses exclusively on the beneficial effects of microbes in food. The section on traditional and modern fermented foods covers the role of microbes and their diversity in fermented foods, interaction between the different microflora present in fermented food products, development of starter cultures to improve the nutritional and sensory quality of fermented foods, and factors and processes affecting the safety of various fermented foods. The second section focuses on microbes in and as functional foods: probiotics, prebiotics and synbiotics.