The size of the bacteria is very small: from 1 to 10-15 microns. To study the structure, features of the reproduction of bacteria became possible only with the development and improvement of optics. For example, according to the nature, the form of accumulations and the features of the vital activity of bacterial cells, scientists can determine what kind of microorganism belongs to it.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.