The ability of cells to adhere to each other and to their environment is the basis for multicellular life. Adhesion occurs via diverse receptors at the surface of cells that bind to specific ligands in their surroundings. Despite the importance of these adhesion receptors, there is a paucity of tools available for precisely controlling their interactions with the environment. To address this limitation, an interdisciplinary team of scientists from the Freiburg Signalling Research Excellence Clusters BIOSS and CIBSS have engineered an adhesion receptor and a complementary synthetic extracellular environment that can be activated by light. This system can be adapted to render other receptor–ligand interactions amenable to precise manipulation with light. The scientists have published their new optogenetic system in Communications Biology.