Cover legend: Ongoing oscillations wax and wane in complex temporal patterns (background). Computational models can be used to explain the quantitative nature of these fluctuations in terms of critical-state dynamics on two levels: neuronal avalanches on short time scales (<100 ms) and temporal correlations of oscillations on long time scales (>1 s). The two sheets depict the phase diagram of inhibitory (x-axis) and excitatory (y-axis) connectivity, and how critical-state dynamics emerge on short (lower sheet) and long (upper sheet) time scales for the same balance of excitation and inhibition (dashed line). We thank Michele Colombo for help with the artwork. For more information, see the article by Poil, Hardstone et al. (pages 9817–9823).