Ecology is the study of the interactions between organisms and their environment. These studies are scientifically challenging, requiring an interdisciplinary approach since ecosystems involve dynamic interactions between the variety of biotic and abiotic components of the system. To identify the full range of variability and evolutionary trends of the systems, the structures and operating processes need be analysed at different spatial and temporal scales. The data provided by these investigations are useful to understand the many traits of natural biodiversity on our planet, the dynamics of ecosystems and their responses to climatic and anthropogenic impacts, promoting assessments for protection. Long Term Ecological Research (LTER) provides the scientific basis for distinguishing the natural dynamics of ecological processes, which occur over long time intervals, from the effects of global trends such as climate change or factors of local influence and disturbance. The availability of long series of ecological and biodiversity data also makes it possible to evaluate the effectiveness of the actions taken to protect and/or restore environments that have undergone adverse impacts due to anthropogenic pressure such as, for example, eutrophication, soil contamination, impact from extreme events, introduction of alien species. The LTER-Italy Network, consisting of 79 sites distributed throughout the country, is characterized by a high diversity of natural environments (comprising terrestrial, marine, inland and transitional water domains) representing a natural laboratory for interdisciplinary studies. Moreover, the activities carried out in the network allow to bridge the gap between researchers, citizens, users and policy makers. The long time-series availability of ecological data from diversified sites, representative of the environmental variability of our Country, enables the monitoring over time of the processes linked to natural and anthropogenic variations. It is staple information to a sustainable planning for the survival of ecosystems, a strategic objective for the economic and social development of our Country. This volume offers an updated overview of the different activities carried out by the LTER-Italy network and of the results acquired during the first 15 years of its establishment in 2006. It is an overview that ranges from historical and popular aspects to political and social facets, focusing on research carried out at the countless observation sites covering a wide range of topics and approaches. The volume, result of a great collective effort, is addressed to all those who are driven by an interest in knowing the diversity and beauty of our environment, along with its many issues.