| Networks of oscillators may reveal an extremely rich variety of unusual dynamical properties, at the microscopic as well as at the collective level. I discuss a couple of examples: (I) extensivity of chaos in generic mean-field models, which includes the anomalous case of the Hamiltonian mean field, where a positive exponent survives in the thermodynamic limit, in spite of the seemingly regular (periodic) behaviour; (ii) the onset of collective chaos in globally coupled and sparse networks. |