There is currently a growing interest in mosses inspired by: 1) Their use as atmospheric air quality biomonitors, 2) their importance as ecological status markers of global changes in hostile environments, and 3) their use in various bioengineering and biotechnological applications. Moreover, additional attention to mosses stems from their importance as the dominant terrestrial plants in high latitudes -- most notably arctic and subarctic regions -- that are subjected to climate warming. This book aims to characterize poorly studied aspects of the chemical composition of inventoried mosses across not only the subarctic, but also the Antarctic regions. This book focuses strongly on mosses inhabiting western and northern Siberia and European Russia, with nine total chapters devoted to these regions. Out of more than 25,000 studies dealing with mosses (from 1950 to 2018), only 300 were devoted to mosses from Siberia (WoS, all databases). This book also focuses on the use of mosses as bioindicators; physio-chemical principles and case studies of applications for tracing industrial pollution are discussed. Additionally, the process of moss biomineralization in a petrifying spring is also considered. Taken together, the twelve chapters presented provide a comprehensive overview of mosses in ecology, biodiversity, biogeochemistry, and mineralogy.