In a handful of soil, there are more microorganisms than there are people in the entire world. When beneficial microbes prevail, plants thrive, and we receive a healthy and bountiful harvest. This principle applies to all areas of the household and determines the condition of water, appliances, and even waste and compost. With the help of effective microorganisms (EM), a positive microbial environment can be achieved. This manual provides a practical introduction with many tips and current case studies. It familiarizes the interested user with the concept and the diverse applications of EM.