Life on Earth thrives on the foundation of healthy soils, including topsoil and subsoil. While extensive research has focused on the topsoil layer, the subsoils remain largely unexplored. By bringing together key experts and practitioners, DeepHorizon aims to unlock knowledge of the subsoil in critical zone in order to deploy ecosystemic solutions to improve subsoil unctions for soil health. DeepHorizon goal is to develop tools that will enable practitioners, land managers and policy makers to access subsoil properties, subsoil functions, soil health indicators and financial decision support tools to promote sustainable subsoil management. By creating its own community of end-users and key stakeholders, DeepHorizon will ultimately promote sustainable management practices, policy-incentives and guidelines at EU level for increasing carbon storage and ecosystem services in subsoils and disseminate and communicate materials to a better understanding of subsoil relevance to the general public. By improving knowledge and consideration of subsoils in general, DeepHorizon will enhance soil health and pave the way for a more sustainable and resilient environment in Europe.