Human interference with the planet has been threatening the stable provision of the ecosystem services on which our society depends. Thus, concerns about the stability of ecosystems are now on the 'agendas' of decision-makers (EU environmental commitments, etc.), religious leaders (Pope Francis' environmental concerns, etc.) and society at large (the movement started by Greta Thunberg, etc.). In terrestrial ecosystems, most ecosystem services are provided directly and indirectly by the soil, such as nutrient and water cycling, biodiversity, pollination, food production, carbon sequestration, climate regulation, etc. And it is the soil biota (bacteria, fungi, nematodes, plant roots, arthropods, earthworms, small mammals, etc.) that are behind all these ecosystem services. When the diversity and abundance of soil biota changes, it affects ecosystem services. This course is designed to give an integrated and up-to-date view of the soil biota and its fundamental role in the functions and services of the ecosystem, our common home.