So, suppose you have a lot of bacteria in the sample which you want to study. It is necessary to take a liquid gnotobiotic environment, more precisely 10 tubes with it. Take a drop of our sample and transfer it to the first tube, then take a drop from the first test-tube and transfer it to the second and so on to 10. With each dilution, the number of microorganisms will decrease, and as a result, if evenly distributed over the surface of a dense agar medium, from the final test tube, in places where the microorganisms hit, after a while large or small colonies will be formed.