Today, routine microbiological analysis of drinking water is based on the growth on nutrient plates to visible colonies of the microbial cells present in a sample. This method requires much time and in many cases underestimates the number of existing germs. Microbial cells can be detected in water samples much more quickly using the method of flow cytometry. The method is flexible and permits, for example, the measurement of the total number of cells within 15 minutes. However, it is also possible to determine the «activity / vitality» of cells, or allows quick screening for specific pathogens. Some of these methods are already being used in practice.