The Asturian Mesolithic, one of the classic periods in the prehistoric investigation of the Iberian Peninsula, is characterised by the formation of large shell middens. Research on this period began in the early 20th century by the Count of Vega del Sella, although it was during the second part of that century when there were significant advances for the knowledge of this period. Recently, new projects have stimulated the study of the last hunter-fisher-gatherers in northern Iberia. Excavations at the shell midden site of El Mazo (Asturias, Spain) have been carried out since 2009. The archaeological intervention has been crucial to determine the formation and erosion processes of the shell midden, the existence of significant climatic changes during the Mesolithic, as well as the technological characteristics, subsistence strategies and the symbolism of human populations. The analysis of the remains of the cemented shell midden, together with the stratigraphic and micromorphological analysis, have been essential for establishing the formation and erosion processes of the mesolithic deposit, as well as to infer its original morphology. In this sense, the shell midden occupied most of the rockshelter, with human occupations progressively occurring from the inside to the outside of the shelter as the shell midden grew. On the other hand, this multidisciplinary perspective has also provided relevant information on the post-depositional processes that have affected the different strata, the different occupation events and the activities carried out on the site. Using various analytical techniques, it has been possible to establish the evolution of climatic conditions, as well as vegetation, throughout the period of occupation of the site. Within the supposed climatic stability of the Early Holocene, various episodes of climate change have been identified, including the cooling event that occurred between 8,200 and 8,000 years ago. The research developed from the study of different archaeological materials has also been essential for understanding the ways of life of the hunter-fisher-gatherers that occupied the site, and especially to introduce new elements of reflection in the interpretation of this period, as in the case of the lithic industry, the shell tools and the use of plants. In general, the pattern of subsistence strategies shows a diversified economy, taking advantage of the various resources available around the site (marine molluscs, fish, crustaceans, echinoderms, terrestrial mammals, plants). This pattern, together with the procurement of fundamentally local lithic raw materials, indicates the existence of reduced mobility, which would probably take place along the coast on the east-west axis, following the natural pathways with that orientation, provided by the coastal platform of this littoral region. The seasonality of mammals and molluscs indicates an intense use of the site, either as a result of continued occupation for several months of the year or of several visits throughout the annual cycle.