Book of the laureate of the prize named after A.N. Severtsov, Academy of Sciences of the USSR, Doctor of Biological Sciences A.V. Yablokova is devoted to phenetics - a new borderline direction of genetics that studies discrete signs, or hair dryers, characteristic of different populations of animals and plants. It tells how these traits can be used to study the composition and dynamics of populations. The significance of the data obtained by phenetics for science and practice is shown: for the study of evolution, the organization of the rational use of commercial species and the protection of animals and plants.