Microorganisms affect everyone. Some are helpful, while others are harmful. Explores pathogenic microorganisms that can cause diseases like sore throats, influenza, tuberculosis, and HIV; decomposer microorganisms that decay rotting plant and animal matter, returning important nutrients back into the soil; and microorganisms that are also being used in the fuel industry to develop new nonpetroleum based products. Overviews food spoilage microorganisms such as mold that can ruin stored food. Explains other bacteria and yeasts are vital to the production of food and drinks like yogurt and bread, along with beer and wine. Examines where they come from and some examples of positive uses relating to many foods we eat.