Immunological synapses (ISs) are specialised signalling domains characterised by complex molecular clustering and segregation at the contact site between cells of the immune system. T lymphocytes form different ISs depending on their state of activation and on the antigen-presenting cells with which they interact. The structural features of the various ISs are better established than the functions they carry out. Recent advances point to the importance of taking into account diversity in both the structures and the functions of IS.