The encyclopedia contains a description of 410 species of medicinal plants, both domestic and foreign, but not all of them have been used for a long time. Only those medicinal plants were selected, which became possible to treat after a thorough study of their chemical composition, confirmation of the pharmacological effect of the detected substances, after many years of research on the search for ways to best prepare the drug and introduce it into the body. This also applied to those plants that have long been listed as medicinal in folk medicine.