Microorganisms are living things too small to see without a microscope, including bacteria, yeasts, molds, algae, and viruses. In food they play three starring roles: as fermenters that make bread, cheese, yogurt, beer, and wine; as spoilage agents that ruin flavor, texture, and appearance; and as pathogens that cause foodborne illness. Managing them through heating, chilling, drying, fermentation, acidification, and sanitation is the central task of food safety and the foundation of nearly every preservation method. Food microbiology studies how each group grows and dies under different conditions so that processes can be designed to favor the useful microbes and eliminate the harmful ones.