This book introduces a literature review of research conducted on Quercus analysed by species, country and topic, and the main biological processes related to the oak's response to global change are reviewed. An extensive review on the uses of acorn oils, flours, extracts, and beverages is presented. The nutritional composition and bioactive compounds naturally present in acorn are described, as well as the effects of their bioactivities on human health. Some research on pollination characteristics and acorn production in determined species of this taxon is examined, highlighting aerobiological data as an important aspect to be considered in reproduction studies. Additionally, deciduous species of the Quercus L. genus are studied during their introduction in the botanical garden of Southern Federal University in Russia. The ecological parameters of 17 species were evaluated, including winter hardiness, drought resistance, phenology, genetic data, and resistance to diseases and pests. The authors aim to determine whether Q. crassipes and Q. castanea can be recognized as foundation species, denoting that both species are dominant oaks of Mexican temperate forests. Next, this compilation discusses the most widely explored phytochemical group in oak leaves, polyphenols, of which condensed and hydrolysable tannins have been reported in high concentrations in different Quercus species. The authors consider the habitat and species diversity of oak forests in Bulgaria. The flora of studied oak forests, their structure and functionality, production, chemistry, intensity of biological turnover, and caloric content of phytomass fractions are presented in detail. An extensive study is conducted to access the population status of Quercus leucotrichophora seedlings in a part of Garhwal Himalaya Oak forest through the establishment of permanent plots in different altitudes.