The investigated plant species Urtica dioica, Taraxacum officinale, Plantago lanceolata, Datura stramonium are characterized by a frequent use as a remedy. In this thesis, I have dealt with medicinal and poisonous plants and their application in the medical and pharmaceutical field. The plants used were selected together with my supervisor. A literature review on the selected plants and their use was made. The use of natural remedies is again becoming increasingly popular. Even in this time, when many drugs can be made synthetically, many natural substances are still used for the manufacture of medicines and ointments. The knowledge of herbal remedies was passed on over generations and was in danger to be forgotten, however, people are again more frequently returning to the natural methods, as our ancestors did. In the experimental part of the thesis the anatomy of the plants was investigated with the help of a light microscope. The microscope images used are intended to provide a look into the interior of plants, since many of the medicinal plants contain important ingredients and cell types which we could not see without this method. The medical relevance and use of medicinal plants was investigated using Urtica dioica, Taraxacum officinale, Plantago lanceolata, Datura stramonium. The use of plants in the industry was briefly discussed. In all investigated plants, a health-promoting effect was shown by diverse ingredients. The Plantago lanceolata was especially beneficial to the respiratory tract, while the nettle has an effect on the urinary tract.