This science paper deals with the diversity of trees growing in Central Europe. Examining the diversity in the European forests is an important factor which enables us to understand the interdependence of the forest ecosystem. In this paper the internal structure, the environmental requirements and the medicinal benefit of five different trees is being analyzed. The five trees examined are the oak, the willow, the birch as representatives of deciduous trees and the pine tree and the larch as representatives of conifers. In order to investigate the internal structure the wood and the leaves were examined under a microscope and the results were compared. Regarding the wood the examination shows a considerably more complex build-up of the deciduous trees compared to the conifers. The broad-leafed trees have a higher diversity in cell types, which are optimized to fulfill the different functions of the tree. The family of the deciduous trees even shows different levels of development. As to the leaves the distinctions can be continued. While the leaves of the conifers have a xeromorph adaption, the foliage of the deciduous trees is optimized for photosynthesis. In investigating the environmental requirements the conclusion is that the broad-leafed trees are more demanding than the conifers. The conifers are quite similar in the medicinal benefit because of the identical active substance “turpentine”. Therefore most of the needle trees are used for respiratory illnesses. The deciduous trees have a greater variety and completely different active ingredients. That is the reason why they can be used for many different diseases. The conclusion to be drawn out of this research paper is the importance of the diversity of the Central European trees for our ecosystem. Every tree has its own unique function and quality and is needed in the interaction within the environment.