Talin has emerged as the key cytoplasmic protein that mediates integrin adhesion to the extracellular matrix. In this Review, we draw on experiments performed in mammalian cells in culture and to present evidence that talin is the most important component of integrin adhesion complexes. We describe how the properties of this adaptor protein enable it to orchestrate integrin adhesions. Talin forms the core of integrin adhesion complexes by linking integrins directly to actin, increasing the affinity of integrin for ligands (integrin activation) and recruiting numerous proteins. It regulates the strength of integrin adhesion, senses matrix rigidity, increases focal adhesion size in response to force and serves as a platform for the building of the adhesion structure. Finally, the mechano-sensitive structure of talin provides a paradigm for how proteins transduce mechanical signals to chemical signals.