Agriculture is the most impactful human activity, inevitably leading to environmental issues. One such crisis is the unprecedented rate at which we deplete our arable lands by growing crops without restoring soils. The trends of soil loss threaten our food security and, to preserve lands, we must transition to a more “circular” agriculture, which returns nutrients to the field. In nature, specialised decomposers implement circularity by recycling organic matter. Among them, earthworms, one of the most abundant animal groups, are pivotal. However, since they hide below ground, scientists only know them very little. This project will finally open the black box by developing modern and original tools, based on sensors and artificial intelligence, that uncover the behaviour and ecology of earthworms. Understanding these cryptic creatures in depth will allow us to best utilise their agricultural services while protecting these key players to preserve and restore our soils.